ANDROID笔记:ImageView的简单使用

package com.example.classtest;

import android.app.Activity;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Matrix;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.ZoomButton;

public class ImageViewActivity extends Activity implements OnClickListener {
    // 透明度取值:0-255
    int alpha = 255;
    ImageView imageView = null;
    float towidth = 1;
    float toheight = 1;
    Bitmap bitmapsrc = null;
    int bwidth;
    int bheight;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.imageview);
        // 缩放按钮
        ZoomButton button3 = (ZoomButton) findViewById(R.id.btn3);
        ZoomButton button4 = (ZoomButton) findViewById(R.id.btn4);
        button3.setOnClickListener(this);
        button4.setOnClickListener(this);
        // 设置透明度的按钮
        Button button1 = (Button) findViewById(R.id.btn1);
        Button button2 = (Button) findViewById(R.id.btn2);
        button1.setOnClickListener(this);
        button2.setOnClickListener(this);
        imageView = (ImageView) findViewById(R.id.image);
        // 得到需要缩放的图片资源
        bitmapsrc = BitmapFactory.decodeResource(getResources(),
                R.drawable.ic_launcher);
        bwidth = bitmapsrc.getWidth();
        bheight = bitmapsrc.getHeight();

    }

    @Override
    public void onClick(View v) {
        Matrix matrix = new Matrix();
        Bitmap bitmap = null;
        switch (v.getId()) {
        case R.id.btn3:
            // 放大图片
            towidth = (float) (towidth * 1.25);
            toheight = (float) (toheight * 1.25);
            // 矩阵计算
            matrix.postScale(towidth, toheight);
            bitmap = Bitmap.createBitmap(bitmapsrc, 0, 0, bwidth, bheight,
                    matrix, true);
            imageView.setImageBitmap(bitmap);
            break;
        case R.id.btn4:
            towidth = (float) (towidth * 0.75);
            toheight = (float) (toheight * 0.75);

            matrix.postScale(towidth, toheight);
            bitmap = Bitmap.createBitmap(bitmapsrc, 0, 0, bwidth, bheight,
                    matrix, true);
            imageView.setImageBitmap(bitmap);
            break;
        case R.id.btn1:
            alpha += 40;
            if (alpha > 255) {
                alpha = 255;
            }
            // 设置图片透明度
            imageView.setAlpha(alpha);
            break;
        case R.id.btn2:
            alpha -= 40;
            if (alpha < 0) {
                alpha = 0;
            }
            imageView.setAlpha(alpha);
            break;

        }

    }
}

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical" >

    <!-- 横向滚动条 -->

    <HorizontalScrollView
        android:layout_width="320px"
        android:layout_height="wrap_content" >

        <!-- 纵向滚动条 -->

        <ScrollView
            android:layout_width="wrap_content"
            android:layout_height="200px" >

            <ImageView
                android:id="@+id/image"
                android:layout_width="wrap_content"
                android:layout_height="350dp"
                android:scaleType="centerInside"
                android:src="@drawable/ic_launcher" />
        </ScrollView>
    </HorizontalScrollView>

    <LinearLayout
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:orientation="horizontal" >

        <Button
            android:id="@+id/btn1"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="增加透明度" />

        <Button
            android:id="@+id/btn2"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="减小透明度" />

    </LinearLayout>

    <LinearLayout
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:orientation="horizontal" >

        <!-- 缩放按钮 -->

        <ZoomButton
            android:id="@+id/btn3"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:src="@android:drawable/btn_plus" />

        <ZoomButton
            android:id="@+id/btn4"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:src="@android:drawable/btn_minus" />
    </LinearLayout>

</LinearLayout>

重点：

　　图片的透明度：imageView.setAlpha(alpha);（alpha 0-255）

　　图片的缩放:    matrix.postScale(towidth, toheight);
            　　　　 bitmap = Bitmap.createBitmap(bitmapsrc, 0, 0, bwidth, bheight, matrix, true);

　　　　　　　　　imageView.setImageBitmap(bitmap);