MainActivity如下:
package cn.testcanvas;
import android.os.Bundle;
import android.widget.ImageView;
import android.app.Activity;
import android.graphics.Bitmap;
import android.graphics.Bitmap.Config;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Rect;
/**
* Demo描述:
* canvas的save()和restore()以及clipRect()方法测试
*
* Demo总结:
* 1 save()和restore()要配对使用(restore可以比save少,但不能多)
* 若restore调用次数比save多,会报错
* 2 canvas剪裁后绘制的东西只能在裁剪区域的范围能才能显示出来
*
* 参考资料:
* http://blog.csdn.net/lonelyroamer/article/details/8264189
*
*
*/
public class MainActivity extends Activity {
private ImageView mImageView;
private ImageView mClipedImageView;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
init();
}
private void init(){
mImageView=(ImageView) findViewById(R.id.imageView);
mClipedImageView=(ImageView) findViewById(R.id.clipedImageView);
//分开测试
//testClip();
testSaveAndRestore();
}
private void testClip(){
Bitmap bitmap=Bitmap.createBitmap(200, 200, Config.ARGB_8888);
Canvas canvas=new Canvas(bitmap);
canvas.drawColor(Color.GREEN);
Paint paint=new Paint();
paint.setColor(Color.YELLOW);
canvas.drawText("绿色部分为Canvas剪切前的区域", 20, 50, paint);
Rect rect=new Rect(10,95,180,140);
canvas.clipRect(rect);
canvas.drawColor(Color.YELLOW);
paint.setColor(Color.BLACK);
//canvas剪裁后绘制的东西只能在裁剪区域的范围能才能显示出来
canvas.drawText("黄色部分为Canvas剪切后的区域", 10, 110, paint);
mImageView.setImageBitmap(bitmap);
//显示截取后的Bitmap:
Bitmap newBitmap=Bitmap.createBitmap(bitmap,10,95,170,45);
mClipedImageView.setImageBitmap(newBitmap);
}
private void testSaveAndRestore(){
Bitmap bitmap=Bitmap.createBitmap(200, 200, Config.ARGB_8888);
Canvas canvas=new Canvas(bitmap);
Paint paint=new Paint();
paint.setColor(Color.RED);
paint.setTextSize(25);
canvas.rotate(15);
canvas.drawText("Hello Android 1", 20, 30, paint);
canvas.translate(50, 50);
//注意:save()方法
//保存在此save()方法之前的canvas的操作
//比如:roate(),translate(),clipXXX()
canvas.save();
paint.setColor(Color.GREEN);
paint.setTextSize(15);
canvas.rotate(60);
canvas.translate(-20,-20);
canvas.drawText("Hello Android 2", 20, 60, paint);
//注意:restore()方法将save()方法之
//后Canvas的roate(),translate(),clipXXX()的操作清空
canvas.restore();
paint.setColor(Color.BLACK);
paint.setTextSize(15);
canvas.drawText("Hello Android 3", 20, 70, 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"
>
<TextView
android:id="@+id/textView"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="测试Canvas"
android:layout_centerHorizontal="true"
/>
<ImageView
android:id="@+id/imageView"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="@id/textView"
android:layout_centerInParent="true"
/>
<ImageView
android:id="@+id/clipedImageView"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="@id/imageView"
android:layout_centerHorizontal="true"
android:layout_marginTop="15dip"
/>
</RelativeLayout>
