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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，超出屏幕怎么辦。下面我們就來看看圖片的放大和縮小吧。

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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、快速移動后松開，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：最后一個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軸的坐標位移大于FLING_MIN_DISTANCE，且移動速度大于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，并拖動，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，尚未松開或拖動，由一個1個MotionEvent ACTION_DOWN觸發 // 注意和onDown()的區別，強調的是沒有松開或者拖動的狀態 @Override public void onShowPress(MotionEvent e) { // TODO Auto-generated method stub Log.i(TAG, "onShowPress..."); } // 用戶（輕觸觸摸屏后）松開，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后的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); /* 因為圖片放到最大時放大按鈕會disable，所以在縮小時把它重設為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后的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); } } } ?

轉載于:https://my.oschina.net/u/555639/blog/226899

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