Android的ImageView介绍-android学习之旅（二十二）

ImageView简介

imageView继承于View，主要用于显示图片，凡是Drawable对象都可以用它显示。
ImageView直接派生了ImageButton和ZoomButton等组件。

ImageView的属性设置

android：sacleType的设置是用来设置图片的显示方式。

图片浏览器实例

package peng.liu.testview;

import android.app.Activity;
import android.graphics.Bitmap;
import android.graphics.drawable.BitmapDrawable;
import android.os.Bundle;
import android.os.SystemClock;
import android.view.MotionEvent;
import android.view.View;
import android.widget.Button;
import android.widget.Chronometer;
import android.widget.ImageView;


public class MainActivity extends Activity implements View.OnClickListener{
    private int[] images = new int[]{
            R.drawable.ic_launcher,
            R.drawable.ic_launcher,
            R.drawable.ic_launcher,
            R.drawable.ic_launcher,
            R.drawable.ic_launcher,
    };
    private int currentImg = 2;
    private int alpha = 0;
    private Button plus,minus,next;
    private ImageView image1,image2;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        plus = (Button) findViewById(R.id.plus);
        minus = (Button) findViewById(R.id.minus);
        next = (Button) findViewById(R.id.next);
        image1 = (ImageView) findViewById(R.id.image1);
        image2 = (ImageView) findViewById(R.id.image2);
        next.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                image1.setImageResource(images[++currentImg%images.length]);
            }
        });
        plus.setOnClickListener(this);
        minus.setOnClickListener(this);
        image1.setOnTouchListener(new View.OnTouchListener() {
            @Override
            public boolean onTouch(View view, MotionEvent motionEvent) {
                BitmapDrawable bitmapDrawable = (BitmapDrawable) image1.getDrawable();
                Bitmap bitmap = bitmapDrawable.getBitmap();
                double scale = bitmap.getWidth()/320.0;
                int x = (int) (motionEvent.getX()*scale);
                int y = (int) (motionEvent.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;
            }
        });
    }

    @Override
    public void onClick(View view) {
        if (view == plus){
            alpha+=20;
        }
        if (view == minus){
            alpha-=20;
        }
        if (alpha>=255){
            alpha = 255;
        }
        if (alpha <= 0){
            alpha = 0;
        }
    }
}

布局代码

<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:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    android:paddingBottom="@dimen/activity_vertical_margin"
    tools:context=".MainActivity"
    android:orientation="vertical">
 <LinearLayout
     android:layout_width="fill_parent"
     android:layout_height="wrap_content"
     android:orientation="horizontal">
     <Button
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:id="@+id/plus"
         android:text="plus"/>
     <Button
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:id="@+id/minus"
         android:text="minus"/>
     <Button
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:id="@+id/next"
         android:text="next"/>
     </LinearLayout>
    <ImageView
        android:layout_width="fill_parent"
        android:layout_height="240dp"
        android:src="@drawable/hello"
        android:id="@+id/image1"/>
    <ImageView
        android:layout_width="120dp"
        android:layout_height="120dp"
        android:src="#f00"
        android:id="@+id/image2"
        android:layout_gravity="center_horizontal"/>
</LinearLayout>

效果图