关于android context 空指针 问题 -问答-阿里云开发者社区-阿里云

开发者社区> 问答> 正文
阿里云
为了无法计算的价值
打开APP
阿里云APP内打开

关于android context 空指针 问题

2016-03-26 11:37:40 3039 1
LoginDialog l=new LoginDialog();

 l.LoginDialog2(M.this);

我写了个LoginDialog类 如下 结果 老是 报错

            public class LoginDialog extends Activity implements OnClickListener {
private Context mcontext=null;
 public void LoginDialog2 (Context context) {  

        this.mcontext = context;  

        LayoutInflater layoutInflater = LayoutInflater.from(context);  
        View longinDialogView = layoutInflater.inflate(MResource.getIdByName(getApplication(), "layout", "logindialog"), null);  

        //获取布局中的控件  
        EditText mUserName = (EditText)longinDialogView.findViewById( MResource.getIdByName(getApplication(), "id", "edit_username"));  
        EditText  mPassword = (EditText)longinDialogView.findViewById( MResource.getIdByName(getApplication(), "id", "edit_password"));  

        //创建一个AlertDialog对话框  
        AlertDialog longinDialog = new AlertDialog.Builder(context)  
            .setTitle("登录框")  
            .setView(longinDialogView)                //加载自定义的对话框式样  
            .setPositiveButton("确定",  this)  
            .setNeutralButton("取消", this)  
            .create();    

        longinDialog.show();
    }
@Override
public void onClick(DialogInterface arg0, int arg1) {
    // TODO Auto-generated method stub

} 


}

错误提示 java.lang.NullPointerException

取消 提交回答
全部回答(1)
  • 爵霸
    2019-07-17 19:15:57

    自定义对话框不是这么搞啊

    MyDialog.java
     package com.antex.assist;
    
    import android.app.Dialog;
    import android.content.Context;
    import android.content.DialogInterface;
    import android.view.LayoutInflater;
    import android.view.View;
    import android.view.ViewGroup.LayoutParams;
    import android.widget.Button;
    import android.widget.ImageView;
    import android.widget.LinearLayout;
    import android.widget.RelativeLayout;
    import android.widget.TextView;
    
    import com.antex.R;
    
    /**
     * <h3>package:</h3> com.antex.assist <br>
     * <h3>file:</h3> MyDialog.java <br>
     * 
     * <h3>Description:自定义dialog</h3><br>
     * <h3>创建时间:</h3>2013-10
     * 
     * 
     * <pre>
     * @author xiaosanyu<br>
     * &nbsp;&nbsp;email: 446251495@qq.com<br>
     * &nbsp;&nbsp;blog:  <a href="http://blog.csdn.net/a87b01c14">http://blog.csdn.net/a87b01c14</a>
     * </pre>
     * 
     */
    
    public class MyDialog extends Dialog {
    
        /**
         * 构造函数
         * 
         * @param context
         *            上下文环境
         * @param theme
         *            主题
         */
        public MyDialog(Context context, int theme) {
            super(context, theme);
        }
    
        /**
         * 构造函数
         * 
         * @param context
         *            上下文环境
         */
        public MyDialog(Context context) {
            super(context);
        }
    
        /**
         * Helper class for creating a custom dialog
         */
        public static class Builder {
            /** 上下文环境 */
            private Context context;
            /** 标题 */
            private String title;
            /** 消息内容 */
            private String message;
            /** 左侧按钮文字 */
            private String positiveButtonText;
            /** 右侧按钮文字 */
            private String negativeButtonText;
            /** 中间按钮文字 */
            private String neutralButtonText;
            /** 子视图 */
            private View contentView;
            /** 标题图标 */
            private int titleimg = 0;
    
            /** 左侧按钮点击监听 */
            private DialogInterface.OnClickListener positiveButtonClickListener;
            /** 中间按钮点击监听 */
    
            private DialogInterface.OnClickListener neutralButtonClickListener;
            /** 右侧按钮点击监听 */
            private DialogInterface.OnClickListener negativeButtonClickListener;
    
            /**
             * 构造器
             * 
             * @param context
             *            上下文环境
             */
            public Builder(Context context) {
                this.context = context;
            }
    
            /**
             * Set the Dialog message from String
             * 
             * @param message
             *            String类型对话框消息
             * @return Builder 是个抽象类。用于抽象创建下属dialog等类
             */
            public Builder setMessage(String message) {
                this.message = message;
                return this;
            }
    
            /**
             * Set the Dialog message from resource
             * 
             * @param message
             *            int型根据ID获取会话框消息
             * @return Builder 是个抽象类。用于抽象创建下属dialog等类
             */
            public Builder setMessage(int message) {
                this.message = (String) context.getText(message);
                return this;
            }
    
            /**
             * Set the Dialog title from resource
             * 
             * @param title
             *            int型根据ID获取对话框标题
             * @return Builder 是个抽象类。用于抽象创建下属dialog等类
             */
            public Builder setTitle(int title) {
                this.title = (String) context.getText(title);
                return this;
            }
    
            /**
             * Set the Dialog titleimg from resource
             * 
             * @param titleimg
             *            对话框图标
             * @return Builder 是个抽象类。用于抽象创建下属dialog等类
             */
            public Builder setIcon(int titleimg) {
                this.titleimg = titleimg;
                return this;
            }
    
            /**
             * Set the Dialog title from String
             * 
             * @param title
             *            String型对话框标题
             * @return Builder 是个抽象类。用于抽象创建下属dialog等类
             */
            public Builder setTitle(String title) {
                this.title = title;
                return this;
            }
    
            /**
             * Set a custom content view for the Dialog. If a message is set, the
             * contentView is not added to the Dialog...
             * 
             * @param v
             *            对话框子视图
             * @return Builer 是个抽象类。用于抽象创建下属dialog等类
             */
            public Builder setContentView(View v) {
                this.contentView = v;
                return this;
            }
    
            /**
             * Set the positive button resource and it's listener
             * 
             * @param positiveButtonText
             *            按钮文本
             * @param listener
             *            按钮点击监听
             * @return Builer 是个抽象类。用于抽象创建下属dialog等类
             */
            public Builder setPositiveButton(int positiveButtonText,
                    DialogInterface.OnClickListener listener) {
                this.positiveButtonText = (String) context
                        .getText(positiveButtonText);
                this.positiveButtonClickListener = listener;
                return this;
            }
    
            /**
             * Set the positive button text and it's listener
             * 
             * @param positiveButtonText
             *            按钮文本
             * @param listener
             *            按钮点击监听
             * @return Builer 是个抽象类。用于抽象创建下属dialog等类
             */
            public Builder setPositiveButton(String positiveButtonText,
                    DialogInterface.OnClickListener listener) {
                this.positiveButtonText = positiveButtonText;
                this.positiveButtonClickListener = listener;
                return this;
            }
    
            /**
             * Set the negative button resource and it's listener
             * 
             * @param negativeButtonText
             *            按钮文本
             * @param listener
             *            按钮点击监听
             * @return Builer 是个抽象类。用于抽象创建下属dialog等类
             */
            public Builder setNegativeButton(int negativeButtonText,
                    DialogInterface.OnClickListener listener) {
                this.negativeButtonText = (String) context
                        .getText(negativeButtonText);
                this.negativeButtonClickListener = listener;
                return this;
            }
    
            /**
             * Set the negative button text and it's listener
             * 
             * @param negativeButtonText
             *            按钮文本
             * @param listener
             *            按钮点击监听
             * @return Builer 是个抽象类。用于抽象创建下属dialog等类
             */
            public Builder setNegativeButton(String negativeButtonText,
                    DialogInterface.OnClickListener listener) {
                this.negativeButtonText = negativeButtonText;
                this.negativeButtonClickListener = listener;
                return this;
            }
    
            /**
             * Set the Neutral button resource and it's listener
             * 
             * @param neutralButtonText
             *            按钮文本
             * @param listener
             *            按钮点击监听
             * @return Builer 是个抽象类。用于抽象创建下属dialog等类
             */
            public Builder setNeutralButton(int neutralButtonText,
                    DialogInterface.OnClickListener listener) {
                this.neutralButtonText = (String) context
                        .getText(neutralButtonText);
                this.negativeButtonClickListener = listener;
                return this;
            }
    
            /**
             * Set the Neutral button text and it's listener
             * 
             * @param neutralButtonText
             *            按钮文本
             * @param listener
             *            按钮点击监听
             * @return Builer 是个抽象类。用于抽象创建下属dialog等类
             */
            public Builder setNeutralButton(String neutralButtonText,
                    DialogInterface.OnClickListener listener) {
                this.neutralButtonText = neutralButtonText;
                this.neutralButtonClickListener = listener;
                return this;
            }
    
            /**
             * Create the custom dialog
             * 
             * @return MyDialog 返回自定义Dialog
             */
            public MyDialog create() {
                LayoutInflater inflater = (LayoutInflater) context
                        .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
                // instantiate the dialog with the custom Theme
                final MyDialog dialog = new MyDialog(context, R.style.MyDialog);
                View layout = inflater.inflate(R.layout.dialog, new LinearLayout(
                        context), false);
                ImageView titleimage = (ImageView) layout
                        .findViewById(R.id.dialog_title_image);
                TextView tv = (TextView) layout.findViewById(R.id.dialog_msg);
                Button positiveButton = (Button) layout
                        .findViewById(R.id.positiveButton);
                Button negativeButton = (Button) layout
                        .findViewById(R.id.negativeButton);
                Button neutralButton = (Button) layout
                        .findViewById(R.id.neutralButton);
                dialog.addContentView(layout, new LayoutParams(
                        LayoutParams.MATCH_PARENT, LayoutParams.WRAP_CONTENT));
                // set the dialog title
                if (title != null)
                    ((TextView) layout.findViewById(R.id.dialog_title))
                            .setText(title);
                if (titleimg != 0)
                    titleimage.setBackgroundResource(titleimg);
                else
                    titleimage.setVisibility(View.GONE);
                // set the confirm button
                if (positiveButtonText != null) {
                    positiveButton.setText(positiveButtonText);
                    if (positiveButtonClickListener != null) {
                        positiveButton
                                .setOnClickListener(new View.OnClickListener() {
                                    @Override
                                    public void onClick(View v) {
                                        positiveButtonClickListener.onClick(dialog,
                                                DialogInterface.BUTTON_POSITIVE);
                                    }
                                });
                    }
                } else {
                    // if no confirm button just set the visibility to GONE
                    positiveButton.setVisibility(View.GONE);
                }
                // set the cancel button
                if (negativeButtonText != null) {
                    negativeButton.setText(negativeButtonText);
                    if (negativeButtonClickListener != null) {
                        negativeButton
                                .setOnClickListener(new View.OnClickListener() {
                                    @Override
                                    public void onClick(View v) {
                                        negativeButtonClickListener.onClick(dialog,
                                                DialogInterface.BUTTON_POSITIVE);
                                    }
                                });
                    }
                } else {
                    // if no confirm button just set the visibility to GONE
                    negativeButton.setVisibility(View.GONE);
                }
    
                // set the neutral button
                if (neutralButtonText != null) {
                    neutralButton.setText(neutralButtonText);
                    LayoutParams lp = positiveButton.getLayoutParams();
                    lp.width = convertDIP2PX(80);
                    positiveButton.setLayoutParams(lp);
                    RelativeLayout.LayoutParams contentLayoutParams = new RelativeLayout.LayoutParams(
                            convertDIP2PX(80),
                            RelativeLayout.LayoutParams.WRAP_CONTENT);
                    contentLayoutParams.leftMargin = convertDIP2PX(15);
                    contentLayoutParams.addRule(RelativeLayout.RIGHT_OF,
                            R.id.neutralButton);
                    negativeButton.setLayoutParams(contentLayoutParams);
                    if (neutralButtonClickListener != null) {
                        neutralButton
                                .setOnClickListener(new View.OnClickListener() {
                                    @Override
                                    public void onClick(View v) {
                                        neutralButtonClickListener.onClick(dialog,
                                                DialogInterface.BUTTON_POSITIVE);
                                    }
                                });
                    }
                } else {
                    // if no neutral button just set the visibility to GONE
                    neutralButton.setVisibility(View.GONE);
                }
                // set the content message
                if (message != null) {
                    tv.setText(message);
                }
                if (contentView != null) {
                    // add the contentView to the dialog body
                    if (message == null || message == "")
                        tv.setVisibility(View.GONE);
                    LinearLayout ll = (LinearLayout) layout
                            .findViewById(R.id.content);
                    // WindowManager manager = (WindowManager) context
                    // .getSystemService(Context.WINDOW_SERVICE);
                    // Display display = manager.getDefaultDisplay();
                    // int width = display.getWidth();
                    LinearLayout.LayoutParams contentLayoutParams = new LinearLayout.LayoutParams(
                            LinearLayout.LayoutParams.MATCH_PARENT,
                            LinearLayout.LayoutParams.WRAP_CONTENT);
                    contentLayoutParams.weight = 0;
                    // contentLayoutParams.gravity=Gravity.CENTER_VERTICAL;
                    contentLayoutParams.leftMargin = 30;
                    contentLayoutParams.rightMargin = 30;
                    contentLayoutParams.topMargin = 10;
                    ll.addView(contentView, contentLayoutParams);
                }
                dialog.setContentView(layout);
                return dialog;
            }
    
            /**
             * 转换dip为px
             * 
             * @param dip
             *            dip大小
             * @return int dip单位转换成px大小
             */
            public int convertDIP2PX(int dip) {
                float scale = context.getResources().getDisplayMetrics().density;
                return (int) (dip * scale + 0.5f);
            }
        }
    }

    布局文件

    dialog.xml
     <?xml version="1.0" encoding="utf-8"?>
    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:background="@drawable/dialog_bg"
        android:gravity="center_horizontal"
        android:orientation="vertical" >
    
        <RelativeLayout
            android:layout_width="fill_parent"
            android:layout_height="wrap_content"
            android:paddingLeft="20dip" >
    
            <ImageView
                android:id="@+id/dialog_title_image"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_marginLeft="15dip"
                android:layout_marginTop="15dip"
                android:background="@drawable/dialog_title_image"
                android:contentDescription="@string/button_back" />
    
            <TextView
                android:id="@+id/dialog_title"
                style="@style/DialogText.Title"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_marginLeft="19dp"
                android:layout_marginTop="20dip"
                android:layout_toRightOf="@+id/dialog_title_image" />
        </RelativeLayout>
    
        <TextView
            android:layout_width="wrap_content"
            android:layout_height="1dip"
            android:layout_marginLeft="10dip"
            android:layout_marginRight="10dip"
            android:layout_marginTop="5dip"
            android:background="@drawable/lins" />
    
        <ScrollView
            android:layout_width="fill_parent"
            android:layout_height="0dip"
            android:layout_weight="1"
            android:fillViewport="true" >
    
            <LinearLayout
                android:id="@+id/content"
                android:layout_width="fill_parent"
                android:layout_height="wrap_content"
                android:orientation="vertical" >
    
                <TextView
                    android:id="@+id/dialog_msg"
                    style="@style/DialogText"
                    android:layout_width="fill_parent"
                    android:layout_height="wrap_content"
                    android:layout_marginLeft="15dip"
                    android:layout_marginRight="5dip"
                    android:layout_marginTop="10dip" />
    
            </LinearLayout>
        </ScrollView>
    
        <RelativeLayout
            android:id="@+id/drl"
            android:layout_width="fill_parent"
            android:layout_height="wrap_content"
            android:gravity="bottom|center_horizontal"
            android:paddingBottom="30dip"
            android:paddingTop="10dip" >
    
            <Button
                android:id="@+id/positiveButton"
                android:layout_width="100dip"
                android:layout_height="wrap_content"
                android:layout_alignParentLeft="true"
                android:background="@drawable/button_selector"
                android:text="@string/button_ok"
                android:textColor="@color/black"
                android:textSize="20sp"
                android:textStyle="bold" />
    
            <Button
                android:id="@+id/neutralButton"
                android:layout_width="80dip"
                android:layout_height="wrap_content"
                android:layout_marginLeft="15dip"
                android:layout_toRightOf="@id/positiveButton"
                android:background="@drawable/button_selector"
                android:textColor="@color/black"
                android:textSize="20sp"
                android:textStyle="bold" />
    
            <Button
                android:id="@+id/negativeButton"
                android:layout_width="100dip"
                android:layout_height="wrap_content"
                android:layout_marginLeft="30dip"
                android:layout_toRightOf="@id/neutralButton"
                android:background="@drawable/button_selector"
                android:text="@string/button_cancel"
                android:textColor="@color/black"
                android:textSize="20sp"
                android:textStyle="bold" />
        </RelativeLayout>
    
    </LinearLayout>
    
    
    style
      <style name="MyDialog" parent="@android:Theme.Dialog">
            <item name="android:windowFrame">@null</item>
            <item name="android:windowNoTitle">true</item>
            <item name="android:windowBackground">@drawable/dialog_bg</item>
            <item name="android:windowIsFloating">true</item>
            <item name="android:windowContentOverlay">@null</item>
        </style>
    
        <style name="DialogText">
            <item name="android:textColor">#FF000000</item>
            <item name="android:textSize">20sp</item>
            <item name="android:textStyle">bold</item>
        </style>
    
        <style name="DialogText.Title">
            <item name="android:textSize">25sp</item>
            <item name="android:textStyle">bold</item>
            <item name="android:textColor">#1E90FF</item>
        </style>

    调用

                MyDialog.Builder customBuilder = new MyDialog.Builder(mContext0);
            LayoutInflater layout =getLayoutInflater();
            View longinDialogView = layout.inflate(R.layout.logindialog, null, false);
    
            //获取布局中的控件  
            EditText mUserName = (EditText)longinDialogView.findViewById( MResource.getIdByName(getApplication(), "id", "edit_username"));  
            EditText  mPassword = (EditText)longinDialogView.findViewById( MResource.getIdByName(getApplication(), "id", "edit_password"));  
      customBuilder.setTitle("").setContentView(view).setPositiveButton(“确定”, new
                    DialogInterface.OnClickListener() {
                        @Override
                        public void onClick(DialogInterface dialog, int which) {
                            dialog.dismiss();
    
    
                        }
                    }).setNegativeButton(“取消”, new DialogInterface.OnClickListener() {
                @Override
                public void onClick(DialogInterface dialog, int which) {
                    dialog.dismiss();
                }
            });
            Dialog dialog = customBuilder.create();
            dialog.show();
    0 0
相关问答

1

回答

Android Studio:如何获取wrap_content +值?

2020-01-07 18:39:52 900浏览量 回答数 1

1

回答

android 里面使用treemap怎么使用?

2018-05-10 20:02:01 2006浏览量 回答数 1

2

回答

Android中Context context=MainActivity.this是什么意义

2016-06-12 08:46:40 3238浏览量 回答数 2

1

回答

【Android】关于如何选择的问题?

2016-06-07 14:30:33 1449浏览量 回答数 1

1

回答

【Android】关于如何选择的问题?

2016-06-03 11:17:57 1436浏览量 回答数 1

1

回答

关于android高德地图的使用

2016-03-18 10:57:25 2570浏览量 回答数 1

1

回答

android 里面关于音量键重写的问题

2016-03-12 11:01:53 1999浏览量 回答数 1

1

回答

关于android Edittext中可以插入相册中的图片

2016-03-12 14:37:47 1588浏览量 回答数 1

1

回答

关于 Android中如何使用Intent打开新界面,并且进行传值

2016-03-05 14:56:12 2088浏览量 回答数 1

1

回答

关于android EditText输密码时怎么把圆点改成*号

2016-03-05 14:21:06 1851浏览量 回答数 1
+关注
2
文章
9426
问答
问答排行榜
最热
最新
相关电子书
更多
低代码开发师(初级)实战教程
立即下载
阿里巴巴DevOps 最佳实践手册
立即下载
冬季实战营第三期:MySQL数据库进阶实战
立即下载