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();
        }
    }
}