Android ImageView 学习

布局文件：<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"   android:orientation="vertical"   android:layout_width="fill_parent"   android:layout_height="fill_parent">   <LinearLayout        android:orientation="horizontal"       android:layout_width="fill_parent"       android:layout_height="wrap_content"       android:gravity = "center">             <Button           android:id="@+id/btn1"          android:layout_width="wrap_content"          android:layout_height="wrap_content"          android:gravity="center"          android:text="@string/btn1_text"/>"      <Button           android:id = "@+id/btn2"          android:layout_width="wrap_content"          android:layout_height="wrap_content"          android:text="@string/btn2_text"/>      <Button          android:id = "@+id/btn3"          android:layout_width="wrap_content"          android:layout_height="wrap_content"          android:text="btn3"/>   </LinearLayout>  <ImageView       android:id = "@+id/imageview1"      android:layout_width = "fill_parent"      android:background = "#0000ff"      android:layout_height = "240px"      android:src = "@drawable/shuangta"      android:scaleType="fitCenter"/>    <ImageView      android:id = "@+id/imageview2"      android:layout_width="120dp"      android:layout_height = "120dp"      android:background = "#0000ff"      android:layout_marginTop = "10dp"/>       </LinearLayout>

代码：

<pre name="code" class="java">package com.example.imageviewtest2;import android.os.Bundle;import android.app.Activity;import android.graphics.Bitmap;import android.graphics.BitmapFactory;import android.graphics.drawable.BitmapDrawable;import android.view.Menu;import android.view.MotionEvent;import android.view.View;import android.view.View.OnClickListener;import android.view.View.OnTouchListener;import android.widget.Button;import android.widget.ImageView;public class MainActivity extends Activity {int image[] = new int[]{R.drawable.qiao,R.drawable.shuangta,R.drawable.lijiang,R.drawable.shui};int currentImage = 2;private int alpha = 255;protected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);final Button btn1 = (Button)findViewById(R.id.btn1);final Button btn2 = (Button)findViewById(R.id.btn2);final ImageView image1 = (ImageView)findViewById(R.id.imageview1);final ImageView image2= (ImageView)findViewById(R.id.imageview2);final Button  btn3 = (Button)findViewById(R.id.btn3);btn3.setOnClickListener(new OnClickListener() {@Overridepublic void onClick(View arg0) {// TODO Auto-generated method stubif(currentImage >=  4){currentImage = 0;}BitmapDrawable bitmapDrawable = (BitmapDrawable)image1.getDrawable();if(!bitmapDrawable.getBitmap().isRecycled()){bitmapDrawable.getBitmap().recycle();}image1.setImageBitmap(BitmapFactory.decodeResource(getResources(), image[currentImage]));currentImage ++;}});OnClickListener listener = new OnClickListener() {@Overridepublic void onClick(View arg0) {// TODO Auto-generated method stub                  if(arg0 == btn1)                  {                  alpha += 20;                  }                  if(arg0 == btn2)                  {                  alpha -= 20;                  }                  if(alpha >= 255)                  {                  alpha = 255;                  }                  if(alpha <= 0)                  {                  alpha = 0;                  }                  image1.setAlpha(alpha);                  }};btn1.setOnClickListener(listener);btn2.setOnClickListener(listener);image1.setOnTouchListener(new OnTouchListener() {@Overridepublic boolean onTouch(View arg0, MotionEvent arg1) {// TODO Auto-generated method stubBitmapDrawable bitmapDrawable = (BitmapDrawable)image1.getDrawable();Bitmap bitmap = bitmapDrawable.getBitmap();double scale = bitmap.getWidth() / 320.0;int x = (int)(arg1.getX()*scale);int y = (int)(arg1.getY()*scale);if(x + 120 > bitmap.getWidth()){x = bitmap.getWidth() - 120;}if(y + 120 > bitmap.getHeight()){y = bitmap.getHeight() - 120;}image2.setImageBitmap(Bitmap.createBitmap(bitmap,x,y,120,120));image2.setAlpha(alpha);return false;}});}@Overridepublic 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;}}