mainActivity如下:
package c.c;
import android.app.Activity;
import android.content.Intent;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.PorterDuffXfermode;
import android.net.Uri;
import android.os.Bundle;
import android.provider.MediaStore;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.ImageView;
/**
* 需求描述:
* 从相册中选取两张图片合成一张图片
*
* 小结:
* 1 依据图片的Uri加载图片
* mBitmap1=BitmapFactory.decodeStream
* (getContentResolver().openInputStream(photoFileUri));
* 为什么使用getContentResolver呢？因为在相册本身是一个内容提供者
* 2 注意构造方法:
* Canvas canvas=new Canvas(bitmap);
* 为什么要传入一个bitmap呢？
* 我们画东西肯定是在画布上画.
* 但是在这里传入一个bitmap
* 即该bitmap是一个载体,相当于把bitmap作为了画布.
* 当然本质上是:把东西画在了canvas里的bitmap上
* 也可以这么想:
* 我们最后不是要用mImageView.setImageBitmap(参数是一个Bitmap)来显示
* 一张图片么？所以在构造Canvas的时候传入了一个Bitmap.然后把两张图片
* 画到了该Bitmap上.最后该Bitmap就是两张照片的合成图.
* 所以当然要把两张图片画到一个Bitmap上
*/
public class MainActivity extends Activity {
private static int REQUESTCODE=0;
private final static int PICK_FIRST_PHOTO=1;
private final static int PICK_SECOND_PHOTO=2;
private boolean isPickedFirstPhoto=false;
private boolean isPickedSecondPhoto=false;
private Button mButton1;
private Button mButton2;
private Bitmap mBitmap1;
private Bitmap mBitmap2;
private ImageView mImageView;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
init();
}
private void init(){
mButton1=(Button) findViewById(R.id.button1);
mButton1.setOnClickListener(new ButtonOnClickListenerImpl());
mButton2=(Button) findViewById(R.id.button2);
mButton2.setOnClickListener(new ButtonOnClickListenerImpl());
mImageView=(ImageView) findViewById(R.id.imageView);
}
private class ButtonOnClickListenerImpl implements OnClickListener{
public void onClick(View v) {
if (v.getId()==R.id.button1) {
REQUESTCODE=PICK_FIRST_PHOTO;
} else {
REQUESTCODE=PICK_SECOND_PHOTO;
}
Intent intent=new Intent(Intent.ACTION_PICK, MediaStore.Images.Media.EXTERNAL_CONTENT_URI);
startActivityForResult(intent, REQUESTCODE);
}
}
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
super.onActivityResult(requestCode, resultCode, data);
if (resultCode==RESULT_OK) {
Uri photoFileUri=data.getData();
if (requestCode==PICK_FIRST_PHOTO) {
try {
mBitmap1=BitmapFactory.decodeStream
(getContentResolver().openInputStream(photoFileUri));
isPickedFirstPhoto=true;
} catch (Exception e) {
e.printStackTrace();
}
}
if (requestCode==PICK_SECOND_PHOTO) {
try {
mBitmap2=BitmapFactory.decodeStream
(getContentResolver().openInputStream(photoFileUri));
isPickedSecondPhoto=true;
} catch (Exception e) {
e.printStackTrace();
}
}
if (isPickedFirstPhoto&&isPickedSecondPhoto) {
Bitmap bitmap=
Bitmap.createBitmap(mBitmap1.getWidth(), mBitmap1.getHeight(), mBitmap1.getConfig());
Canvas canvas=new Canvas(bitmap);
Paint paint=new Paint();
canvas.drawBitmap(mBitmap1, 0, 0, paint);
paint.setXfermode(new PorterDuffXfermode(android.graphics.PorterDuff.Mode.MULTIPLY));
canvas.drawBitmap(mBitmap2, 0, 0,paint);
mImageView.setImageBitmap(bitmap);
}
}
}
}
main.xml如下:
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent" >
<Button
android:id="@+id/button1"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_centerHorizontal="true"
android:text="选择第一张图片"
/>
<Button
android:id="@+id/button2"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_centerHorizontal="true"
android:layout_below="@id/button1"
android:text="选择第二张图片"
/>
<ImageView
android:id="@+id/imageView"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_centerInParent="true"
android:layout_below="@id/button2"
/>
</RelativeLayout>
