Android 图片放大缩小

在android中，图片的放大和缩小是很重要的一个方法，我们主要用到的就是bitmap、MotionEvent
、Matrix、KeyEvent、OnTouchListene、ImageView。还有很多，在做图片的放大和缩小我们要知道的是， 取得屏幕分辨率大小，始化相关变量，还要定义的是图片缩小和放大的比例，我们还得判断图片太大，超出屏幕怎么办。下面我们就来看看图片的放大和缩小吧。

 

package EOE.android; 

import Android.app.Activity; 
import android.graphics.Bitmap; 
import android.graphics.BitmapFactory; 
import android.graphics.Color; 
import android.graphics.Matrix; 
import android.os.Bundle; 
import android.util.DisplayMetrics; 
import android.util.Log; 
import android.view.GestureDetector; 
import android.view.KeyEvent; 
import android.view.MotionEvent; 
import android.view.View; 
import android.view.GestureDetector.OnGestureListener; 
import android.view.View.OnTouchListener; 
import android.widget.Button; 
import android.widget.FrameLayout; 
import android.widget.ImageView; 
import android.widget.LinearLayout; 
import android.widget.Toast; 

public class DisplayImage extends Activity implements OnTouchListener, OnGestureListener { 
private static final String TAG = "DisplayImage"; 
private static final int FLING_MIN_DISTANCE = 100; 
private static final int FLING_MIN_VELOCITY = 200; 


/* 相关变量声明 */ 
private ImageView mImageView; 
private Button mButton01; 
private Button mButton02; 
private FrameLayout layout1; 
private LinearLayout layoutImage; 
private Bitmap bmp; 
private int id=0; 
private int displayWidth; 
private int displayHeight; 
private float scaleWidth=1; 
private float scaleHeight=1; 
private GestureDetector mGestureDetector; 

/** Called when the activity is first created. */ 
@Override 
public void onCreate(Bundle savedInstanceState) { 
super.onCreate(savedInstanceState); 
/* 加载display.xml Layout */ 
setContentView(R.layout.display); 

/* 取得屏幕分辨率大小 */ 
DisplayMetrics dm=new DisplayMetrics(); 
getWindowManager().getDefaultDisplay().getMetrics(dm); 
displayWidth=dm.widthPixels; 
displayHeight=dm.heightPixels; 

/* 初始化相关变量 */ 
Bundle bundle = this.getIntent().getExtras(); 
Integer imageId = bundle.getInt("imageId"); 
Log.i(TAG, "onCreate, imageId = " + imageId); 

bmp=BitmapFactory.decodeResource(getResources(), imageId); 
mImageView = (ImageView)findViewById(R.id.myImageView); 
mImageView.setImageBitmap(bmp); 
mImageView.setOnTouchListener(this); 
mImageView.setLongClickable(true); 

layout1 = (FrameLayout)findViewById(R.id.layout1); 
layoutImage = (LinearLayout)findViewById(R.id.layoutImage); 
mButton01 = (Button)findViewById(R.id.myButton1); 
mButton02 = (Button)findViewById(R.id.myButton2); 

/* 缩小按钮onClickListener */ 
mButton01.setOnClickListener(new Button.OnClickListener() { 
@Override 
public void onClick(View v) { 
small(); 
} 
}); 

/* 放大按钮onClickListener */ 
mButton02.setOnClickListener(new Button.OnClickListener() { 
@Override 
public void onClick(View v) { 
big(); 
} 
}); 
} 

// 用户轻触触摸屏，由1个MotionEvent ACTION_DOWN触发 
@Override 
public boolean onDown(MotionEvent e) { 
// TODO Auto-generated method stub 
// Toast.makeText(this, "onDown", Toast.LENGTH_SHORT).show(); 
Log.i(TAG, "onDown..."); 

return false; 
} 

/* 用户按下触摸屏、快速移动后松开，由1个MotionEvent ACTION_DOWN, 
* 多个ACTION_MOVE, 1个ACTION_UP触发 
* 参数解释： 
* e1：第1个ACTION_DOWN MotionEvent 
* e2：最后一个ACTION_MOVE MotionEvent 
* velocityX：X轴上的移动速度，像素/秒 
* velocityY：Y轴上的移动速度，像素/秒 
* 触发条件 ： 
* X轴的坐标位移大于FLING_MIN_DISTANCE，且移动速度大于FLING_MIN_VELOCITY个像素/秒 
* @see android.view.GestureDetector$OnGestureListener#onFling(android.view.MotionEvent, android.view.MotionEvent, float, float) 
*/ 
@Override 
public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, 
float velocityY) { 
// TODO Auto-generated method stub 
Log.i(TAG, "onFling..."); 

if (e1.getX() - e2.getX() > FLING_MIN_DISTANCE 
&& Math.abs(velocityX) > FLING_MIN_VELOCITY) { 
// Fling left 

Toast.makeText(this, "Fling Left", Toast.LENGTH_SHORT).show(); 
} else if (e2.getX() - e1.getX() > FLING_MIN_DISTANCE 
&& Math.abs(velocityX) > FLING_MIN_VELOCITY) { 

// Fling right 

Toast.makeText(this, "Fling Right", Toast.LENGTH_SHORT).show(); 
} 

return false; 
} 

// 用户长按触摸屏，由多个MotionEvent ACTION_DOWN触发 
@Override 
public void onLongPress(MotionEvent e) { 
// TODO Auto-generated method stub 
Log.i(TAG, "onLongPress..."); 

} 

// 用户按下触摸屏，并拖动，由1个MotionEvent ACTION_DOWN, 多个ACTION_MOVE触发 
@Override 
public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, 
float distanceY) { 
// TODO Auto-generated method stub 
Log.i(TAG, "onScroll..."); 

return false; 
} 

// 用户轻触触摸屏，尚未松开或拖动，由一个1个MotionEvent ACTION_DOWN触发 
// 注意和onDown()的区别，强调的是没有松开或者拖动的状态 
@Override 
public void onShowPress(MotionEvent e) { 
// TODO Auto-generated method stub 
Log.i(TAG, "onShowPress..."); 

} 

// 用户（轻触触摸屏后）松开，由一个1个MotionEvent ACTION_UP触发 
@Override 
public boolean onSingleTapUp(MotionEvent e) { 
// TODO Auto-generated method stub 
Log.i(TAG, "onSingleTapUp..."); 

return false; 
} 

@Override 
public boolean onTouch(View v, MotionEvent event) { 
// TODO Auto-generated method stub 
Log.i(TAG, "onTouch..."); 

// Set button visible 
mButton01.setVisibility(View.VISIBLE); 
mButton02.setVisibility(View.VISIBLE); 

return mGestureDetector.onTouchEvent(event); 
} 

// @Override 
// public boolean onTouchEvent(MotionEvent event) { 
// // TODO Auto-generated method stub 
// super.onTouchEvent(event); 
// 
// Log.i(TAG, "onTouchEvent"); 
// // Set button visible 
// mButton01.setVisibility(View.VISIBLE); 
// mButton02.setVisibility(View.VISIBLE); 
// 
// return true; 
// } 

@Override 
public boolean onKeyDown(int keyCode, KeyEvent event) { 
// TODO Auto-generated method stub 
super.onKeyDown(keyCode, event); 

Log.i(TAG, "onKeyDown..."); 
// Set button visible 
mButton01.setVisibility(View.VISIBLE); 
mButton02.setVisibility(View.VISIBLE); 

return true; 
} 

/* 图片缩小的method */ 
private void small() { 
int bmpWidth=bmp.getWidth(); 
int bmpHeight=bmp.getHeight(); 

Log.i(TAG, "bmpWidth = " + bmpWidth + ", bmpHeight = " + bmpHeight); 

/* 设置图片缩小的比例 */ 
double scale=0.8; 
/* 计算出这次要缩小的比例 */ 
scaleWidth=(float) (scaleWidth*scale); 
scaleHeight=(float) (scaleHeight*scale); 
/* 产生reSize后的Bitmap对象 */ 
Matrix matrix = new Matrix(); 
matrix.postScale(scaleWidth, scaleHeight); 
Bitmap resizeBmp = Bitmap.createBitmap(bmp,0,0,bmpWidth, 
bmpHeight,matrix,true); 

if(id==0) { 
/* 如果是第一次按，就删除原来默认的ImageView */ 
layoutImage.removeView(mImageView); 
} else { 
/* 如果不是第一次按，就删除上次放大缩小所产生的ImageView */ 
layoutImage.removeView((ImageView)findViewById(id)); 
} 

/* 产生新的ImageView，放入reSize的Bitmap对象，再放入Layout中 */ 
id++; 
ImageView imageView = new ImageView(this); 
imageView.setId(id); 
imageView.setImageBitmap(resizeBmp); 
layoutImage.addView(imageView); 
Log.i(TAG, "imageView.getWidth() = " + imageView.getWidth() 
+ ", imageView.getHeight() = " + imageView.getHeight()); 
setContentView(layout1); 
/* 因为图片放到最大时放大按钮会disable，所以在缩小时把它重设为enable */ 
mButton02.setEnabled(true); 
mButton02.setTextColor(Color.MAGENTA); 
} 

/* 图片放大的method */ 
private void big() { 
int bmpWidth=bmp.getWidth(); 
int bmpHeight=bmp.getHeight(); 

Log.i(TAG, "bmpWidth = " + bmpWidth + ", bmpHeight = " + bmpHeight); 

/* 设置图片放大的比例 */ 
double scale=1.25; 
/* 计算这次要放大的比例 */ 
scaleWidth=(float)(scaleWidth*scale); 
scaleHeight=(float)(scaleHeight*scale); 
/* 产生reSize后的Bitmap对象 */ 
Matrix matrix = new Matrix(); 
matrix.postScale(scaleWidth, scaleHeight); 
Bitmap resizeBmp = Bitmap.createBitmap(bmp,0,0,bmpWidth, 
bmpHeight,matrix,true); 

if(id==0) { 
/* 如果是第一次按，就删除原来设置的ImageView */ 
layoutImage.removeView(mImageView); 
} else { 
/* 如果不是第一次按，就删除上次放大缩小所产生的ImageView */ 
layoutImage.removeView((ImageView)findViewById(id)); 
} 

/* 产生新的ImageView，放入reSize的Bitmap对象，再放入Layout中 */ 
id++; 
ImageView imageView = new ImageView(this); 
imageView.setId(id); 
imageView.setImageBitmap(resizeBmp); 
layoutImage.addView(imageView); 
setContentView(layout1); 
/* 如果再放大会超过屏幕大小，就把Button disable */ 
if( scaleWidth * scale * bmpWidth > bmpWidth * 3 || 
scaleHeight * scale * bmpHeight > bmpWidth * 3 || 
scaleWidth * scale * bmpWidth > displayWidth * 5 || 
scaleHeight * scale * bmpHeight > displayHeight * 5) { 
mButton02.setEnabled(false); 
mButton02.setTextColor(Color.GRAY); 
} else { 
mButton02.setEnabled(true); 
mButton02.setTextColor(Color.MAGENTA); 
} 
} 

}