Android画布Canvas的save()和restore()以及clipRect()方法测试
MainActivity如下:
[java] view plaincopy
- 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:
[html] view plaincopy
- <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>
