Android开发实现的图片浏览功能示例【放大图片】

<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"  xmlns:app="http://schemas.android.com/apk/res-auto"  xmlns:tools="http://schemas.android.com/tools"  android:layout_width="match_parent"  android:layout_height="match_parent"  tools:context=".MainActivity"  android:orientation="vertical">  <LinearLayout    android:layout_width="match_parent"    android:layout_height="wrap_content"    android:orientation="horizontal">    <Button      android:id="@+id/plus"      android:layout_width="wrap_content"      android:layout_height="wrap_content"      android:text="增加透明度"      android:layout_weight="1"/>    <Button      android:id="@+id/minus"      android:layout_width="wrap_content"      android:layout_height="wrap_content"      android:text="减少透明度"      android:layout_weight="1"/>    <Button      android:id="@+id/next"      android:layout_width="wrap_content"      android:layout_height="wrap_content"      android:text="下一张"      android:layout_weight="1"/>  </LinearLayout>  <!--此处显示图片整体-->  <ImageView    android:id="@+id/imagel"    android:layout_width="wrap_content"    android:layout_height="280dp"    android:src="@drawable/xiaochouyu"    android:scaleType="fitCenter"/>  <ImageView    android:id="@+id/image2"    android:layout_width="200dp"    android:layout_height="200dp"    android:background="#00f"    android:layout_margin="5dp"/></LinearLayout>

public class MainActivity extends AppCompatActivity {  //定义一个访问图片的数组  int[] images = new int[]{      R.drawable.xiaochouyu ,      R.drawable.leidayu ,      R.drawable.paodangyu ,      R.drawable.huangjindiao ,      R.drawable.piaopiao  };  //定义默认显示的图片  int currentImg = 2 ;  //定义图片初始透明度  private int alpha = 255 ;  @Override  protected void onCreate(Bundle savedInstanceState) {    super.onCreate(savedInstanceState);    setContentView(R.layout.activity_main);    final Button plus = (Button) findViewById(R.id.plus) ;    final Button minus = (Button) findViewById(R.id.minus) ;    final Button next = (Button) findViewById(R.id.next) ;    final ImageView imageView01 = (ImageView) findViewById(R.id.imagel);    final ImageView imageView02 = (ImageView) findViewById(R.id.image2);    //定义查看下一张图片的监听器    next.setOnClickListener(new View.OnClickListener() {      @Override      public void onClick(View v) {        //显示下一张图片        imageView01.setImageResource(images[currentImg++ % images.length]);      }    });    //定义改变图片透明度的方法    View.OnClickListener listener = new View.OnClickListener() {      @RequiresApi(api = Build.VERSION_CODES.JELLY_BEAN)      @Override      public void onClick(View v) {        if (v == plus){          alpha = alpha + 20 ;        }        if (v == minus){          alpha = alpha - 20 ;        }        if (alpha >= 255){          alpha = 255 ;        }        if (alpha <= 0){          alpha = 0 ;        }        imageView01.setImageAlpha(alpha);      }    };    //为两个按钮添加监听器    plus.setOnClickListener(listener);    minus.setOnClickListener(listener);    imageView01.setOnTouchListener(new View.OnTouchListener() {      @RequiresApi(api = Build.VERSION_CODES.JELLY_BEAN)      @Override      public boolean onTouch(View v, MotionEvent event) {        BitmapDrawable bitmapDrawable = (BitmapDrawable) imageView01.getDrawable();        //获取第一个托片显示框中的位图        Bitmap bitmap = bitmapDrawable.getBitmap();        //bitmap图片实际大小与第一个Imageview的缩放比例        double scale = 1.0 * bitmap.getHeight() / imageView01.getHeight();        //获取需要显示的图片开始点        int x = (int) (event.getX() * scale);        int y = (int) (event.getY() * scale);        if (x + 120 > bitmap.getWidth()){          x = bitmap.getWidth() - 120 ;        }        if (y + 120 > bitmap.getHeight()){          y = bitmap.getHeight() - 120 ;        }        //显示图片的指定区域        imageView02.setImageBitmap(Bitmap.createBitmap(bitmap , x , y , 120 , 120));        imageView02.setImageAlpha(alpha);        return false;      }    });  }}