Android DragImageView實現下拉拖動圖片放大效果

發布時間：2020-09-01 22:56:21 來源：腳本之家閱讀：264 作者：宇宙無敵超級羅欄目：移動開發

DragImageView下拉拖動圖片放大，先上圖：

主要的類：繼承了RelativeLayout，再在RelativeLayout里面添加ImageView，通過Touch事件來改變ImageView的縮放，縮放時計算scale，使其在手指移動到屏幕底部時，圖片底部也剛好到達屏幕底部，手指松開時，圖片逐步回彈。

package com.example.dragimagescale; 
 
import android.annotation.SuppressLint; 
import android.app.Activity; 
import android.content.Context; 
import android.content.res.TypedArray; 
import android.graphics.Bitmap; 
import android.graphics.BitmapFactory; 
import android.graphics.Matrix; 
import android.graphics.PointF; 
import android.os.Handler; 
import android.os.Message; 
import android.util.AttributeSet; 
import android.util.DisplayMetrics; 
import android.util.Log; 
import android.view.MotionEvent; 
import android.view.WindowManager; 
import android.widget.ImageView; 
import android.widget.ImageView.ScaleType; 
import android.widget.RelativeLayout; 
 
public class DragScaleImageView extends RelativeLayout { 
 private String TAG = "DragScaleImageView"; 
 private static final int BACK_SCALE = 1010; 
 
 private Context mContext; 
 private AttributeSet attrs; 
 private int displayWidth = 0; 
 private int displayHeight = 0; 
 private int mImageId; 
 private Bitmap bmp; 
 private ImageView imageView; 
 
 /** 是否處在回彈狀態 */ 
 private boolean isBacking = false; 
 
 /** 用于記錄拖拉圖片移動的坐標位置 */ 
 private Matrix matrix = new Matrix(); 
 /** 用于記錄圖片要進行拖拉時候的坐標位置 */ 
 private Matrix currentMatrix = new Matrix(); 
 private Matrix defaultMatrix = new Matrix(); 
 /** 圖片的寬高 */ 
 private float imgHeight, imgWidth; 
 /** 初始狀態 */ 
 private int mode = 0; 
 /** 拖拉照片模式 */ 
 private final int MODE_DRAG = 1; 
 
 private float scaleY = 0; 
 
 /** 用于記錄開始時候的坐標位置 */ 
 private PointF startPoint = new PointF(); 
 
 /** 用于記錄開始時候的在整個屏幕中的Y坐標位置 */ 
 private float startRawY = 0; 
 float scale = 1; 
    
 private TouchEventListener touchEventListener = null; 
 private BackScaleListener backScaleListener = null; 
 
 public DragScaleImageView(Context context, AttributeSet attrs) { 
  super(context, attrs); 
  // TODO Auto-generated constructor stub 
  this.mContext = context; 
  this.attrs = attrs; 
  initView(); 
 } 
 
 public DragScaleImageView(Context context) { 
  super(context); 
  // TODO Auto-generated constructor stub 
  this.mContext = context; 
  initView(); 
 } 
 
 public DragScaleImageView(Activity activity, Bitmap resBitmap, int width, 
   int height) { 
  super(activity); 
 } 
 
 /** 
  * 初始化圖片 
  */ 
 private void initView() { 
  /* 取得屏幕分辨率大小 */ 
  DisplayMetrics dm = new DisplayMetrics(); 
  WindowManager mWm = (WindowManager) mContext 
    .getSystemService(Context.WINDOW_SERVICE); 
  mWm.getDefaultDisplay().getMetrics(dm); 
  displayWidth = dm.widthPixels; 
  displayHeight = dm.heightPixels; 
 
  TypedArray a = mContext.obtainStyledAttributes(attrs, 
    R.styleable.DragScaleImageView); 
  mImageId = a.getResourceId(R.styleable.DragScaleImageView_scale_image, 
    0); 
  a.recycle(); 
  if (null == bmp && mImageId != 0) { 
   bmp = BitmapFactory.decodeResource(getResources(), mImageId); 
   float scale = (float) displayWidth / (float) bmp.getWidth();// 1080/1800 
   matrix.postScale(scale, scale, 0, 0); 
   imgHeight = scale * bmp.getHeight(); 
   imgWidth = scale * bmp.getWidth(); 
  } else { 
   imgHeight = displayWidth; 
   imgWidth = displayWidth; 
  } 
  initImageView(); 
 } 
 
 private void initImageView() { 
  imageView = new ImageView(mContext); 
  imageView.setImageMatrix(matrix); 
  defaultMatrix.set(matrix); 
  Log.w(TAG, "imgWidth :" + imgWidth); 
  Log.w(TAG, "imgHeight :" + imgHeight); 
 
  RelativeLayout.LayoutParams layoutParams = new RelativeLayout.LayoutParams( 
    (int) imgWidth, (int) imgHeight); 
  imageView.setLayoutParams(layoutParams); 
  imageView.setImageBitmap(bmp); 
  imageView.setScaleType(ScaleType.CENTER_CROP); 
  this.addView(imageView); 
 } 
 
 /** 
  * 設置ImageView的寬高 
  * 
  * @param width 
  * @param height 
  */ 
 public void setImageWidthAndHeight(int width, int height) { 
  imgWidth = width; 
  imgHeight = height; 
  RelativeLayout.LayoutParams layoutParams = new RelativeLayout.LayoutParams( 
    (int) imgWidth, (int) imgHeight); 
  imageView.setLayoutParams(layoutParams); 
 } 
 
 public boolean onTouchEvent(MotionEvent event) { 
  Log.w(TAG, "onTouchEvent :" + event.getAction()); 
  // 當該View放置在ScrollView里面時，會與父控件Touch事件沖突，所以touch該控件區域時，父控件不可用 
  if (event.getAction() == MotionEvent.ACTION_UP) { 
   getParent().requestDisallowInterceptTouchEvent(false); 
  } else { 
   getParent().requestDisallowInterceptTouchEvent(true);// true表示父類的不可用; 
  } 
  switch (event.getAction() & MotionEvent.ACTION_MASK) { 
  // 手指壓下屏幕 
  case MotionEvent.ACTION_DOWN: 
   if (isBacking) { 
    return super.onTouchEvent(event); 
   } 
   int[] location = new int[2]; 
   imageView.getLocationInWindow(location); 
   if (location[1] >= 0) { 
    mode = MODE_DRAG; 
    // 記錄ImageView當前的移動位置 
    currentMatrix.set(imageView.getImageMatrix()); 
    startPoint.set(event.getX(), event.getY()); 
    startRawY = event.getRawY(); 
    Log.w(TAG, "onTouchEvent startRawY:" + startRawY); 
   } 
   break; 
  // 手指在屏幕上移動，改事件會被不斷觸發 
  case MotionEvent.ACTION_MOVE: 
   // 拖拉圖片 
   if (mode == MODE_DRAG) { 
//    float dx = event.getX() - startPoint.x; // 得到x軸的移動距離 
    float dy = event.getY() - startPoint.y; // 得到y軸的移動距離 
    // 在沒有移動之前的位置上進行移動 
    if (dy > 0) { 
     matrix.set(currentMatrix); 
     Log.w(TAG, "onTouchEvent dy:" + dy); 
     scale = ((dy / (displayHeight - startRawY) * (displayHeight - imgHeight)) + imgHeight) 
       / imgHeight; // 得到縮放倍數，當手指移動到屏幕底部時，圖片也達到屏幕底部 
     Log.w(TAG, "onTouchEvent scale:" + scale); 
     
     scaleY = dy; 
     RelativeLayout.LayoutParams relativeLayout = new RelativeLayout.LayoutParams( 
       (int) (scale * imgWidth), (int) (scale * imgHeight)); 
     imageView.setLayoutParams(relativeLayout); 
     matrix.postScale(scale, scale, imgWidth / 2, 0); 
     imageView.setImageMatrix(matrix); 
    } 
   } 
   break; 
  // 手指離開屏幕 
  case MotionEvent.ACTION_UP: 
   // 當觸點離開屏幕，圖片還原 
   mHandler.sendEmptyMessage(BACK_SCALE); 
  case MotionEvent.ACTION_POINTER_UP: 
   // 當兩個手指移動時，取消移動圖片 
   mode = 0; 
   break; 
  } 
  // 設置的Touch監聽事件 
  if (touchEventListener != null) { 
   touchEventListener.onTouchEvent(event); 
  } 
  return true; 
 } 
  
 /** 逐步回彈 */ 
 @SuppressLint("HandlerLeak") 
 private Handler mHandler = new Handler() { 
  @Override 
  public void handleMessage(Message msg) { 
   // TODO Auto-generated method stub 
   switch (msg.what) { 
   case BACK_SCALE: 
    scale = (scaleY / 2 + imgHeight) / (imgHeight);// 得到縮放倍數 
    if (scaleY > 0) { 
     isBacking = true; 
     matrix.set(currentMatrix); 
     RelativeLayout.LayoutParams relativeLayout = new RelativeLayout.LayoutParams( 
       (int) (scale * imgWidth), (int) (scale * imgHeight)); 
     imageView.setLayoutParams(relativeLayout); 
     matrix.postScale(scale, scale, imgWidth / 2, 0); 
     imageView.setImageMatrix(matrix); 
     scaleY = (float) (scaleY / 2 - 1); 
     mHandler.sendEmptyMessageDelayed(BACK_SCALE, 20);// 逐步回彈 
    } else { 
     scaleY = 0; 
     RelativeLayout.LayoutParams relativeLayout = new RelativeLayout.LayoutParams( 
       (int) imgWidth, (int) imgHeight); 
     imageView.setLayoutParams(relativeLayout); 
     matrix.set(defaultMatrix); 
     imageView.setImageMatrix(matrix); 
     isBacking = false; 
    } 
    if (backScaleListener != null) { 
     backScaleListener.onBackScale(); 
    } 
    break; 
   default: 
    break; 
   } 
   super.handleMessage(msg); 
  } 
 }; 
  
 public void setTouchEventListener(TouchEventListener touchEventListener) { 
  this.touchEventListener = touchEventListener; 
 } 
  
 public void setBackScaleListener(BackScaleListener backScaleListener) { 
  this.backScaleListener = backScaleListener; 
 } 
 
 /** Touch事件監聽 */ 
 public interface TouchEventListener { 
  public void onTouchEvent(MotionEvent event); 
 } 
 /** 回彈事件監聽 */ 
 public interface BackScaleListener { 
  public void onBackScale(); 
 } 
}

調用的Activity：

package com.example.dragimagescale; 
 
import com.example.dragimagescale.DragScaleImageView.BackScaleListener; 
import com.example.dragimagescale.DragScaleImageView.TouchEventListener; 
 
import android.app.Activity; 
import android.os.Bundle; 
import android.view.MotionEvent; 
 
public class MainActivity extends Activity { 
 
  
 DragScaleImageView mDragScaleImageView; 
  
 @Override 
 protected void onCreate(Bundle savedInstanceState) { 
  super.onCreate(savedInstanceState); 
  setContentView(R.layout.activity_main); 
 
  mDragScaleImageView = (DragScaleImageView) findViewById(R.id.dragScaleImageView); 
  /** 自定義ImageView的寬高，若不設置則按圖片寬高壓縮至屏幕寬度 */ 
//  mDragScaleImageView.setImageWidthAndHeight(720, 300); 
  // Touch事件監聽 
  mDragScaleImageView.setTouchEventListener(new TouchEventListener() { 
    
   @Override 
   public void onTouchEvent(MotionEvent event) { 
    // TODO Auto-generated method stub 
    // do something here 
   } 
  }); 
  // 回彈事件監聽 
  mDragScaleImageView.setBackScaleListener(new BackScaleListener() { 
    
   @Override 
   public void onBackScale() { 
    // TODO Auto-generated method stub 
    // do something here 
   } 
  }); 
 } 
 
  
  
  
 
}

xml 布局文件：

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" 
 xmlns:tools="http://schemas.android.com/tools" 
 xmlns:dragscaleimageview="http://schemas.android.com/apk/res/com.example.dragimagescale" 
 android:layout_width="match_parent" 
 android:layout_height="match_parent" 
 android:background="#ffffff" > 
 
 <com.example.dragimagescale.DragScaleImageView 
  android:id="@+id/dragScaleImageView" 
  android:layout_width="match_parent"   
  android:layout_height="wrap_content" 
  dragscaleimageview:scale_image="@drawable/image" 
  > 
 </com.example.dragimagescale.DragScaleImageView> 
 
</RelativeLayout>

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Android DragImageView實現下拉拖動圖片放大效果

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