自定义View实现图片的绘制、旋转、缩放

1、图片

把一张JPG图片改名为image.jpg，然后拷贝到项目的res-drawable中。

2、activity_main.xml

 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
     android:id="@+id/imageid"
     android:layout_width="fill_parent"
     android:layout_height="fill_parent"
     android:orientation="vertical">

     <Button android:id="@+id/buttonLeft"
         android:text="图片向左移动"
         android:layout_width="fill_parent"
         android:layout_height="wrap_content" />
     <Button android:id="@+id/buttonRight"
         android:text="图片向右移动"
         android:layout_width="fill_parent"
         android:layout_height="wrap_content"/>
     <Button android:id="@+id/buttonRotationLeft"
         android:text="图片向左旋转"
         android:layout_width="fill_parent"
         android:layout_height="wrap_content" />
     <Button android:id="@+id/buttonRotationRight"
         android:text="图片向右旋转"
         android:layout_width="fill_parent"
         android:layout_height="wrap_content" />
     <Button android:id="@+id/buttonNarrow"
         android:text="图片缩小"
         android:layout_width="fill_parent"
         android:layout_height="wrap_content" />
     <Button android:id="@+id/buttonEnlarge"
         android:text="图片放大"
         android:layout_width="fill_parent"
         android:layout_height="wrap_content" />

 </LinearLayout>

 import android.app.Activity;
 import android.os.Bundle;
 import android.view.View;
 import android.content.Context;
 import android.graphics.Paint;
 import android.graphics.Bitmap;
 import android.graphics.BitmapFactory;
 import android.graphics.Matrix;
 import android.graphics.Canvas;
 import android.widget.LinearLayout;
 import android.widget.Button;

 public class MainActivity extends Activity {
     ImageView imageView = null;

     @Override
     protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         setContentView(R.layout.activity_main);

         //    动态加载图片到LinearLayout中
         imageView = new ImageView(this);
         LinearLayout ll = (LinearLayout) findViewById(R.id.imageid);
         ll.addView(imageView);
         //    向左移动
         Button btnLeft = (Button) findViewById(R.id.buttonLeft);
         btnLeft.setOnClickListener(new View.OnClickListener() {
             @Override
             public void onClick(View arg0) {
                 // TODO Auto-generated method stub
                 imageView.setPosLeft();
             }
         });
         //    向右移动
         Button btnRight = (Button) findViewById(R.id.buttonRight);
         btnRight.setOnClickListener(new View.OnClickListener() {
             @Override
             public void onClick(View arg0) {
                 // TODO Auto-generated method stub
                 imageView.setPosRight();
             }
         });

         //    向左旋转
         Button btnRotationLeft = (Button)findViewById(R.id.buttonRotationLeft);
         btnRotationLeft.setOnClickListener(new View.OnClickListener() {
             @Override
             public void onClick(View arg0) {
                 // TODO Auto-generated method stub
                 imageView.setRotationLeft();
             }
         });
         //    向右旋转
         Button btnRotationRight = (Button)findViewById(R.id.buttonRotationRight);
         btnRotationRight.setOnClickListener(new View.OnClickListener() {
             @Override
             public void onClick(View arg0) {
                 // TODO Auto-generated method stub
                 imageView.setRotationRight();
             }
         });

         //    放大图片
         Button btnEnlarge = (Button)findViewById(R.id.buttonEnlarge);
         btnEnlarge.setOnClickListener(new View.OnClickListener() {
             @Override
             public void onClick(View arg0) {
                 // TODO Auto-generated method stub
                 imageView.setEnlarge();
             }
         });
         //    缩小图片
         Button btnNarrow = (Button)findViewById(R.id.buttonNarrow);
         btnNarrow.setOnClickListener(new View.OnClickListener() {
             @Override
             public void onClick(View arg0) {
                 // TODO Auto-generated method stub
                 imageView.setNarrow();
             }
         });
     }

     //    自定义图片View
     class ImageView extends View {
         private Paint paint = null;    //    画笔
         private Bitmap bitmap = null;    //    图片位图
         private Bitmap bitmapDisplay = null;
         private Matrix matrix = null;
         private int nBitmapWidth = 0;    //    图片的宽度
         private int nBitmapHeight = 0;    //    图片的高度
         private int nPosX = 120;    //    图片所在的位置X
         private int nPosY = 10;    //    图片所在的位置Y
         private float fAngle = 0.0f;    //    图片旋转
         private float fScale = 1.0f;    //    图片缩放 1.0表示为原图

         public ImageView(Context context) {
             super(context);

             paint = new Paint();
             paint.setFlags(Paint.ANTI_ALIAS_FLAG);

             //    加载需要操作的图片
             bitmap = BitmapFactory.decodeResource(getResources(), R.drawable.image);
             bitmapDisplay = bitmap;

             matrix = new Matrix();
             //    获取图片高度和宽度
             nBitmapWidth = bitmap.getWidth();
             nBitmapHeight = bitmap.getHeight();
         }

         //    向左移动
         public void setPosLeft() {
             nPosX -= 10;
         }
         //    向右移动
         public void setPosRight() {
             nPosX += 10;
         }

         //    向左旋转
         public void setRotationLeft() {
             fAngle--;
             setAngle();
         }
         //    向右旋转
         public void setRotationRight() {
             fAngle++;
             setAngle();
         }

         //    图片放大
         public void setEnlarge() {
             if (fScale < 2) {
                 fScale += 0.1f;
                 setScale();
             }
         }
         //    图片缩小
         public void setNarrow() {
             if (fScale > 0.5) {
                 fScale -= 0.1f;
                 setScale();
             }
         }

         //    设置旋转比例
         private void setAngle() {
             matrix.reset();
             matrix.setRotate(fAngle);
             bitmapDisplay = Bitmap.createBitmap(bitmap,0,0,nBitmapWidth,nBitmapHeight,matrix,true);
         }

         //    设置缩放比例
         private void setScale() {
             matrix.reset();
             matrix.postScale(fScale, fScale);
             bitmapDisplay = Bitmap.createBitmap(bitmap,0,0,nBitmapWidth,nBitmapHeight,matrix,true);
         }

         @Override
         protected void onDraw(Canvas canvas) {
             super.onDraw(canvas);
             canvas.drawBitmap(bitmapDisplay, nPosX, nPosY, paint);
             invalidate();
         }
     }
 }