Android 圖片放大縮小

在android中，圖片的放大和縮小是很重要的一個方法，我們主要用到的就是bitmap、MotionEvent
、Matrix、KeyEvent、OnTouchListene、ImageView。還有很多，在做圖片的放大和縮小我們要知道的是， 取得屏幕分辨率大小，始化相關變量，還要定義的是圖片縮小和放大的比例，我們還得判斷圖片太大，超出屏幕怎麼辦。下面我們就來看看圖片的放大和縮小吧。

 

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; 


/* 相關變量聲明 */ 
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); 
/* 加載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; 

/* 初始化相關變量 */ 
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); 

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

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

// 用戶輕觸觸摸屏，由1個MotionEvent ACTION_DOWN觸發 
@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; 
} 

/* 用戶按下觸摸屏、快速移動後鬆開，由1個MotionEvent ACTION_DOWN, 
* 多個ACTION_MOVE, 1個ACTION_UP觸發 
* 參數解釋： 
* e1：第1個ACTION_DOWN MotionEvent 
* e2：最後一個ACTION_MOVE MotionEvent 
* velocityX：X軸上的移動速度，像素/秒 
* velocityY：Y軸上的移動速度，像素/秒 
* 觸發條件 ： 
* X軸的座標位移大於FLING_MIN_DISTANCE，且移動速度大於FLING_MIN_VELOCITY個像素/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; 
} 

// 用戶長按觸摸屏，由多個MotionEvent ACTION_DOWN觸發 
@Override 
public void onLongPress(MotionEvent e) { 
// TODO Auto-generated method stub 
Log.i(TAG, "onLongPress..."); 

} 

// 用戶按下觸摸屏，並拖動，由1個MotionEvent ACTION_DOWN, 多個ACTION_MOVE觸發 
@Override 
public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, 
float distanceY) { 
// TODO Auto-generated method stub 
Log.i(TAG, "onScroll..."); 

return false; 
} 

// 用戶輕觸觸摸屏，尚未鬆開或拖動，由一個1個MotionEvent ACTION_DOWN觸發 
// 注意和onDown()的區別，強調的是沒有鬆開或者拖動的狀態 
@Override 
public void onShowPress(MotionEvent e) { 
// TODO Auto-generated method stub 
Log.i(TAG, "onShowPress..."); 

} 

// 用戶（輕觸觸摸屏後）鬆開，由一個1個MotionEvent ACTION_UP觸發 
@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; 
} 

/* 圖片縮小的method */ 
private void small() { 
int bmpWidth=bmp.getWidth(); 
int bmpHeight=bmp.getHeight(); 

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

/* 設置圖片縮小的比例 */ 
double scale=0.8; 
/* 計算出這次要縮小的比例 */ 
scaleWidth=(float) (scaleWidth*scale); 
scaleHeight=(float) (scaleHeight*scale); 
/* 產生reSize後的Bitmap對象 */ 
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，就刪除原來默認的ImageView */ 
layoutImage.removeView(mImageView); 
} else { 
/* 如果不是第一次按，就刪除上次放大縮小所產生的ImageView */ 
layoutImage.removeView((ImageView)findViewById(id)); 
} 

/* 產生新的ImageView，放入reSize的Bitmap對象，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); 
/* 因爲圖片放到最大時放大按鈕會disable，所以在縮小時把它重設爲enable */ 
mButton02.setEnabled(true); 
mButton02.setTextColor(Color.MAGENTA); 
} 

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

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

/* 設置圖片放大的比例 */ 
double scale=1.25; 
/* 計算這次要放大的比例 */ 
scaleWidth=(float)(scaleWidth*scale); 
scaleHeight=(float)(scaleHeight*scale); 
/* 產生reSize後的Bitmap對象 */ 
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，就刪除原來設置的ImageView */ 
layoutImage.removeView(mImageView); 
} else { 
/* 如果不是第一次按，就刪除上次放大縮小所產生的ImageView */ 
layoutImage.removeView((ImageView)findViewById(id)); 
} 

/* 產生新的ImageView，放入reSize的Bitmap對象，再放入Layout中 */ 
id++; 
ImageView imageView = new ImageView(this); 
imageView.setId(id); 
imageView.setImageBitmap(resizeBmp); 
layoutImage.addView(imageView); 
setContentView(layout1); 
/* 如果再放大會超過屏幕大小，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); 
} 
} 

}