UI复习-组件:ImageView(图片缩放)-优快云博客

本文介绍了一个基于Android的示例应用，该应用通过触摸屏幕实现图片的缩放及局部展示，并展示了如何使用Android的触摸事件处理机制来获取触摸坐标，计算缩放比例，并在另一个ImageView中显示所选区域。

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package com.brady.est;

import android.annotation.SuppressLint;
import android.graphics.Bitmap;
import android.graphics.drawable.BitmapDrawable;
import android.os.Bundle;
import android.support.v7.app.ActionBarActivity;
import android.view.Menu;
import android.view.MenuItem;
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;
import android.widget.TextView;

@SuppressLint({ "HandlerLeak", "ClickableViewAccessibility" })
public class MainActivity extends ActionBarActivity {

    private int[] images = new int[]{R.drawable.a,R.drawable.b,R.drawable.c,R.drawable.d};
    int currentImage = 0;
    
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        
        final Button button = (Button)findViewById(R.id.button);
        final ImageView imageView1 = (ImageView)findViewById(R.id.image1);
        final ImageView imageView2 = (ImageView)findViewById(R.id.image2);
        final TextView detail = (TextView)findViewById(R.id.detail);
        
        
        button.setOnClickListener(new OnClickListener() {
            
            @Override
            public void onClick(View v) {
                imageView1.setImageResource(images[currentImage%images.length]);
                currentImage++;
            }
        });
        
        imageView1.setOnTouchListener(new OnTouchListener() {
            
            @Override
            public boolean onTouch(View v, MotionEvent event) {
                
                BitmapDrawable bitmapDrawable =  (BitmapDrawable)imageView1.getDrawable();
                Bitmap bitmap = bitmapDrawable.getBitmap();
                
                //缩放比例
                double scale = bitmap.getWidth()/imageView1.getWidth();
                
                int x = (int)(event.getX()*scale);
                int y = (int)(event.getY()*scale);
                if(x+150>bitmap.getWidth()){
                    x = bitmap.getWidth()-150;
                }
                
                if(y+100>bitmap.getHeight()){
                    y = bitmap.getHeight()-150;
                }
                detail.setText(scale+"\n"+"x:"+x+"\n"+bitmap.getWidth()+"\n"+"y:"+y+"\n"+bitmap.getHeight());
                imageView2.setImageBitmap(Bitmap.createBitmap(bitmap, x, y, 100, 100));
                
                return false;
            }
        });
        
    }

    @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 action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();
        if (id == R.id.action_settings) {
            return true;
        }
        return super.onOptionsItemSelected(item);
    }
}

布局XML文件

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
      android:orientation="vertical"
    android:id="@+id/root"
    android:padding="5dip"
    tools:context="com.brady.est.MainActivity" >
     
    <ImageView 
        android:id="@+id/image1"
        android:layout_width="200px"
        android:layout_height="wrap_content"
        android:src="@drawable/a"/>
    <Button
        android:id="@+id/button"
        android:text="下一张"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        />
    <ImageView 
        android:id="@+id/image2"
        android:layout_width="120px"
        android:layout_height="wrap_content"
        />
    <TextView 
        android:id="@+id/detail"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"/>
 
</LinearLayout>