寫一個 ImageViewHelper 來處理圖片放大縮小等功能 (matrix)
上次小弟有介紹 使用gridview 顯示相簿中的縮圖 http://blog.maxkit.com.tw/2014/01/android-gridview.html 在當時的範例中提到，我們可以點擊縮相簿中的縮圖，將圖片放大顯示，這部份主要是透過ImageView的來實現，但是看來看去就覺得「它很陽春」，沒錯，真的很陽春。 我們還可以做點什麼功能呢？ 是的，一般的相本功能中，顯示圖片時不是可以放大縮小，還可以拖拉位置嗎？ 後來發現android 提供了一個matrix的元件，可以用來實現Scale image, 我們在上次的project中，再增加一個ImageViewHelper.java檔案，帶入imageview來擴充它的功能。
ImageViewHelper.java
package com.example.gridview;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.Matrix;
import android.graphics.PointF;
import android.graphics.RectF;
import android.util.DisplayMetrics;
import android.util.FloatMath;
import android.view.MotionEvent;
import android.view.View;
import android.view.View.OnTouchListener;
import android.widget.ImageView;
public class ImageViewHelper {
private ImageView imageView;
private Matrix matrix = new Matrix();
private Matrix savedMatrix = new Matrix();
private Bitmap bitmap;
private static final int NONE = 0;// 初始狀態
private static final int DRAG = 1;// 拖曳狀態
private static final int ZOOM = 2;// 縮放狀態
private int mode = NONE;
private int lastaction = 0;
private PointF pA = new PointF();
private PointF pB = new PointF();
private PointF prev = new PointF();
private PointF mid = new PointF();
private PointF lastClickPos = new PointF();
private float dist = 1f;
private DisplayMetrics dm;
private float minScaleR = 0.1f; // 最少缩放比例
private static final float MAX_SCALE = 10f; // 最大缩放比例
private static final float DOUBLECLICK_SCALE = 2f; // 雙擊放大比例
long lastClickTime = 0;
float viewW;
float viewH;
private long down_time = 0;
/**
* 紀錄圖片狀態是否超出螢幕
*/
private boolean isZoom;
public ImageViewHelper(DisplayMetrics dm, ImageView imageView, Bitmap bitmap) {
this. dm = dm;
this. imageView = imageView;
this. bitmap = bitmap;
setImageSize();
minZoom();
center();
imageView.setImageMatrix( matrix);
isZoom = false;
}
public Matrix getMatrix() {
return matrix;
}
// 取得最小的比例, 假設圖片比螢幕大
// 則螢幕(寬/長)/圖片(寬/長)會小於1 那麼也就是將圖片進行縮小
// 反之 則進行放大 而圖片越小 放大倍數則會越大
// 如果螢幕跟圖片大小相同 則倍數會為1 即不變
public void minZoom() {
Context c = imageView .getContext();
minScaleR = Math. min(
( float) dm. widthPixels / ( float) bitmap.getWidth(),
( float) dm. heightPixels / ( float) bitmap.getHeight());
if ( minScaleR > 1) {
minScaleR = 1;
}
matrix.postScale( minScaleR, minScaleR);
}
public void center() {
center( true, true);
}
// 橫向、縱向置中
public void center(boolean horizontal, boolean vertical) {
Matrix m = new Matrix();
m.set( matrix);
RectF rect = new RectF(0, 0, bitmap.getWidth(), bitmap.getHeight());
m.mapRect(rect);
float height = rect.height();
float width = rect.width();
float deltaX = 0, deltaY = 0;
isZoom = true;
if (vertical) {
// 圖片小於螢幕大小，則置中顯示。
// 大於螢幕，上方則留空白則往上移，下方留空白則往下移
int screenHeight = dm. heightPixels;
if (height < screenHeight) {
deltaY = (screenHeight - height) / 2 - rect.top;
isZoom = false;
} else if (rect. top > 0) {
deltaY = -rect. top;
} else if (rect. bottom < screenHeight) {
deltaY = imageView.getHeight() - rect.bottom;
}
}
if (horizontal) {
int screenWidth = dm. widthPixels;
if (width < screenWidth) {
deltaX = (screenWidth - width) / 2 - rect.left;
isZoom = false;
} else if (rect. left > 0) {
deltaX = -rect. left;
} else if (rect. right < screenWidth) {
deltaX = screenWidth - rect. right;
}
}
matrix.postTranslate(deltaX, deltaY);
}
// 兩點的距離
public float spacing(MotionEvent event) {
float x = event.getX(0) - event.getX(1);
float y = event.getY(0) - event.getY(1);
return FloatMath. sqrt(x * x + y * y);
}
public float spacing( float x1, float y1, float x2, float y2) {
float x = x1 - x2;
float y = y1 - y2;
return FloatMath. sqrt(x * x + y * y);
}
// 兩點的中點
public void midPoint(PointF point, MotionEvent event) {
float x = event.getX(0) + event.getX(1);
float y = event.getY(0) + event.getY(1);
point.set(x / 2, y / 2);
}
protected void doubleClick( float x, float y) {
float p[] = new float[9];
matrix.getValues(p);
if ( mode == DRAG) {
if (p[0] > minScaleR) {
matrix.setScale( minScaleR, minScaleR);
} else {
matrix.setScale( DOUBLECLICK_SCALE, DOUBLECLICK_SCALE, x, y);
}
center();
}
imageView.setImageMatrix( matrix);
}
// 限制最大最小缩放比例
protected void CheckScale() {
float p[] = new float[9];
matrix.getValues(p);
if ( mode == ZOOM) {
if (p[0] < minScaleR) {
matrix.setScale( minScaleR, minScaleR);
}
if (p[0] > MAX_SCALE) {
matrix.set( savedMatrix);
}
}
}
// 建立圖片移動縮放事件
public void setImageSize() {
imageView.setOnTouchListener( new OnTouchListener() {
@Override
public boolean onTouch(View arg0, MotionEvent event) {
switch (event.getAction() & MotionEvent.ACTION_MASK) {
case MotionEvent. ACTION_DOWN:
savedMatrix.set( matrix);
prev.set(event.getX(), event.getY());
// pA.set(event.getX(), event.getY());
// pB.set(event.getX(), event.getY());
mode = DRAG; // 設定為拖拉模式
down_time = System.currentTimeMillis();
break;
case MotionEvent. ACTION_POINTER_DOWN:
dist = spacing(event);
// 如果兩點距離超過10, 就判斷為多點觸控模式 即為縮放模式
if (spacing(event) > 10f) {
savedMatrix.set( matrix);
midPoint( mid, event);
mode = ZOOM;
}
break;
case MotionEvent. ACTION_UP:
case MotionEvent. ACTION_POINTER_UP:
if ( mode == DRAG) {
long now = System.currentTimeMillis();
if ((now - lastClickTime) < 300) {
Context c = imageView.getContext();
// Toast.makeText(c, "click time:" + (now -
// lastClickTime) , Toast.LENGTH_SHORT).show();
doubleClick(event.getX(), event.getY());
now = 0;
} else {
if (now - down_time >= 300
&& now - down_time < 1000) {
Context c = imageView.getContext();
}
}
lastClickTime = now;
}
mode = NONE;
break;
case MotionEvent. ACTION_MOVE:
if ( mode == DRAG && isZoom) { // 超出圖片
// if (isZoom) { // 超出圖片
matrix.set( savedMatrix);
matrix.postTranslate(event.getX() - prev. x,
event.getY() - prev. y);
// matrix.postTranslate(event.getX() - prev.x, 0);
arg0.getParent().requestDisallowInterceptTouchEvent(
true); // 父類別onTouch()不可使用,圖片放大後才能左右查看圖片
} else if ( mode == ZOOM) {
float newDist = spacing(event);// 偵測兩根手指移動的距離
if (newDist > 10f) {
matrix.set( savedMatrix);
float tScale = newDist / dist;
matrix.postScale(tScale, tScale, mid. x, mid. y);
}
}
break;
}
imageView.setImageMatrix( matrix);
CheckScale(); // 限制缩放范围
center();
lastaction = event.getAction();
return true;
}
});
}
}
這個檔案實作後，原來的MainActivity.java 還是得調整一下
package com.example.gridview;
import java.util.ArrayList;
import java.util.List;
import android.app.Activity;
import android.content.ClipData.Item;
import android.content.ContentResolver;
import android.database.Cursor;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.Bundle;
import android.provider.MediaStore;
import android.util.DisplayMetrics;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.GridView;
import android.widget.ImageView;
public class MainActivity extends Activity {
private GridView gridView ;
private ImageView imageView;
private List<String> thumbs;
private List<String> imagePaths;
private ImageAdapter imageAdapter;
private Item photos;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout. activity_main);
gridView = (GridView) findViewById(R.id. gridView1);
imageView = (ImageView) findViewById(R.id.imageView1 );
ContentResolver cr = getContentResolver();
String[] projection = { MediaStore.Images.Media. _ID,
MediaStore.Images.Media. DATA };
Cursor cursor = cr.query(MediaStore.Images.Media.EXTERNAL_CONTENT_URI ,
projection, null, null, null);
thumbs = new ArrayList<String>();
imagePaths = new ArrayList<String>();
for ( int i = 0; i < cursor.getCount(); i++) {
cursor.moveToPosition(i);
int id = cursor.getInt(cursor
.getColumnIndex(MediaStore.Images.Media. _ID)); // �Y��ID
thumbs.add(id + "");
String filepath = cursor.getString(cursor
.getColumnIndex(MediaStore.Images.Media. DATA));
imagePaths.add(filepath);
}
cursor.close();
imageAdapter = new ImageAdapter(MainActivity. this, thumbs);
gridView .setAdapter(imageAdapter );
imageAdapter.notifyDataSetChanged();
// imageView.setOnClickListener(new OnClickListener() {
//
// @Override
// public void onClick(View v) {
// // TODO Auto-generated method stub
// imageView.setVisibility(View.GONE);
// gridView.setVisibility(View.VISIBLE);
// }
//
// });
imageView.setVisibility(View. GONE);
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu. main, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle item selection
switch (item.getItemId()) {
case R.id. action_photos:
imageView.setVisibility(View. GONE);
gridView .setVisibility(View. VISIBLE);
return true;
default:
return super.onOptionsItemSelected(item);
}
}
public void setImageView( int position) {
Bitmap bm = BitmapFactory.decodeFile( imagePaths.get(position));
imageView.setImageBitmap(bm);
imageView.setVisibility(View. VISIBLE);
gridView .setVisibility(View. GONE);
DisplayMetrics dm = this.getResources().getDisplayMetrics();
new ImageViewHelper(dm, imageView, bm);
}
}
我在ImageViewHelper的 imageView.setOnTouchListener 加上了雙點還原、放大及兩點放大縮小的事件, 於是MainActivity的imageView.setOnClickListener 就失效了，於是我把它onclick的事件移除，用menu的按鈕來取代。
menu的作法請看程式碼中 onCreateOptionsMenu(Menu menu) {…} 、onOptionsItemSelected(MenuItem item) {...} 這兩段。
main.xml請放到res/menu的資料中
< menu xmlns:android= "http://schemas.android.com/apk/res/android" >
<item
android:id= "@+id/action_photos"
android:orderInCategory= "100"
android:showAsAction= "never"
android:title= "@string/action_photos" />
</ menu>
如果你做到這裡發現........... 根本就不能放大縮小嘛！ 那可能是跟我一樣忽略了一個地方 請檢查xml中imageview的設定屬性，是否少了一個 ## android:scaleType = "matrix" ##，好，趕快加上去再試試看吧。
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