利用Matrix類旋轉位圖(bitmap)

本練習利用Matrix類的setRotate()方法, 通過Bitmap.createBitmap()方法從一個源位圖創建另一個複製的位圖, 從而做到旋轉的效果.



main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    >
<TextView  
    android:layout_width="fill_parent" 
    android:layout_height="wrap_content" 
    android:text="@string/hello"
    />
<LinearLayout 
    android:orientation="horizontal"
    android:layout_width="fill_parent" 
    android:layout_height="wrap_content" 
    android:gravity="center_horizontal"
    >
<SeekBar   
    android:layout_width="fill_parent"   
    android:layout_height="wrap_content"   
    android:layout_margin="10px"  
    android:id="@+id/rotatebar"  
    android:max="360" 
    android:progress="0"  
    />  
</LinearLayout>
<ImageView  
 android:id="@+id/imageview"
 android:layout_gravity="center"
    android:layout_width="fill_parent" 
    android:layout_height="fill_parent" 
    android:scaleType="center"
    />
</LinearLayout>

AndroidImage.java

package com.AndroidImage;

import android.app.Activity;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Matrix;
import android.os.Bundle;
import android.widget.ImageView;
import android.widget.SeekBar;

public class AndroidImage extends Activity {
 
 private ImageView myImageView;
 private float scale, rotateDegree;
 private Bitmap bitmap;
 int bmpWidth, bmpHeight;
 SeekBar rotateBar;
 
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        
        myImageView = (ImageView)findViewById(R.id.imageview);
        rotateBar = (SeekBar)findViewById(R.id.rotatebar);

        bitmap = BitmapFactory.decodeResource(getResources(), R.drawable.icon);
        bmpWidth = bitmap.getWidth();
        bmpHeight = bitmap.getHeight();
        scale = 1;
        rotateDegree = 0;
        
        loadImage();

        rotateBar.setOnSeekBarChangeListener(new SeekBar.OnSeekBarChangeListener() {
   
   @Override
   public void onStopTrackingTouch(SeekBar seekBar) {
    // TODO Auto-generated method stub
   }
   
   @Override
   public void onStartTrackingTouch(SeekBar seekBar) {
    // TODO Auto-generated method stub
   }
   
   @Override
   public void onProgressChanged(SeekBar seekBar, int progress,
     boolean fromUser) {
    // TODO Auto-generated method stub
    rotateDegree = (float)progress;
    loadImage();
   }
  });
    }
    
    private void loadImage(){

     Matrix matrix = new Matrix();
     matrix.postScale(scale, scale);
     matrix.setRotate(rotateDegree);
     
     Bitmap scaledBitmap = Bitmap.createBitmap(bitmap, 0, 0, bmpWidth, bmpHeight, matrix, true);
     myImageView.setImageBitmap(scaledBitmap);

    }
}