刚开始安卓，记录一个刚做的图片缩放程序

刚开始做安卓，写了一个简陋的图片缩放程序。费了一点时间，看来还是有必要记录下来。

布局代码：

<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:layout_gravity="clip_vertical" >
    <LinearLayout
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
        android:gravity="bottom|center_horizontal"
        android:orientation="horizontal" >
        <Button
            android:id="@+id/bsx"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="缩小" />
        <Button
            android:id="@+id/bfd"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="放大" />
    </LinearLayout>
    <LinearLayout
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:orientation="vertical" >
        <ImageView
            android:id="@+id/img"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content" >
        </ImageView>
    </LinearLayout>
</FrameLayout>

java代码：

package com.example.myscalepic;

import android.os.Bundle;
import android.app.Activity;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Matrix;
import android.util.DisplayMetrics;
import android.util.Log;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.Toast;

public class MainActivity extends Activity implements OnClickListener {
    ImageView imgView;
    Bitmap bmp;
    int screenWidth; //屏幕宽度
    int screenHeight;//屏幕高度
    float scaleWidth = 1f; //缩放倍率
    float scaleHeight = 1f;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        bmp = BitmapFactory.decodeResource(getResources(), R.drawable.feng);
        DisplayMetrics dm = new DisplayMetrics();
        getWindowManager().getDefaultDisplay().getMetrics(dm);
        screenWidth = dm.widthPixels;
        screenHeight = dm.heightPixels - 80;
        imgView = (ImageView) this.findViewById(R.id.img);
        Button b1 = (Button) this.findViewById(R.id.bsx);
        Button b2 = (Button) this.findViewById(R.id.bfd);
        //设置图片
        imgView.setImageBitmap(bmp);
        b1.setOnClickListener(this);
        b2.setOnClickListener(this);
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.activity_main, menu);
        return true;
    }

    @Override
    public void onClick(View v) {

        if (v.getId() == R.id.bfd) {//点击放大按钮
            scaleWidth *= 1.2;
            scaleHeight *= 1.2;
        } else { //点击缩小按钮
            scaleWidth *= 0.8;
            scaleHeight *= 0.8;
        }
        //设置新的图片
        imgView.setImageBitmap(scaleToFit());
    }

    /**
     * 缩放函数
     * @return
     */
    private Bitmap scaleToFit() {
        int width = bmp.getWidth();
        int height = bmp.getHeight();
        Matrix ma = new Matrix();
        ma.postScale(scaleWidth, scaleHeight);
        Bitmap tewmpmap;
        if (width * scaleWidth > screenWidth|| height * scaleHeight > screenHeight) {
            scaleWidth=1f;
            scaleHeight=1f;
            return bmp;
        } else {
            //得到图片缩放后的副本
            tewmpmap = Bitmap.createBitmap(bmp, 0, 0, width, height, ma, true);
            return tewmpmap;
        }
    }
}