MainAcitivy.java

package com.example.sample_4_22;import java.util.ArrayList;import java.util.List;import android.app.Activity;import android.app.ProgressDialog;import android.database.Cursor;import android.graphics.Bitmap;import android.graphics.BitmapFactory;import android.graphics.Matrix;import android.os.AsyncTask;import android.os.Bundle;import android.provider.MediaStore;import android.provider.MediaStore.Images;import android.util.DisplayMetrics;import android.util.Log;import android.view.View;import android.view.View.OnClickListener;import android.view.Window;import android.widget.Button;import android.widget.ImageView;public class MainActivity extends Activity {    String fpath;    List<String> filesPath;    ImageView imageView;    Button bt;    Button bt2;    Button bt3;    int i = 0;    ProgressDialog dialog;    float scalex = 1;    float scaley = 1;    int imageX;    int imageY;    int widthorig;    int heightorig;    Bitmap firstmap;    Bitmap bitmap;    float degrees =10;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        requestWindowFeature(Window.FEATURE_NO_TITLE);        setContentView(R.layout.activity_main);        filesPath = new ArrayList<String>();        imageView = (ImageView) findViewById(R.id.imageView1);        imageView.setMaxHeight(500);        bt = (Button) findViewById(R.id.button1);        bt2 = (Button) findViewById(R.id.button2);        bt3 = (Button) findViewById(R.id.button3);        dialog = new ProgressDialog(this);        dialog.setMessage("正在加载中...");        DisplayMetrics dm = new DisplayMetrics();        getWindowManager().getDefaultDisplay().getMetrics(dm);        imageX = dm.widthPixels;        imageY = dm.heightPixels - 200;        Cursor cursor = getContentResolver().query(                MediaStore.Images.Media.EXTERNAL_CONTENT_URI, null, null, null,                Images.Media.BUCKET_DISPLAY_NAME);        if (cursor != null) {            cursor.moveToFirst();            while (cursor.moveToNext()) {                fpath = cursor.getString(cursor                        .getColumnIndexOrThrow(MediaStore.Images.Media.DATA));                filesPath.add(fpath);            }        }        firstmap = BitmapFactory.decodeFile(filesPath.get(0));        imageView.setImageBitmap(firstmap);        widthorig = firstmap.getWidth();        heightorig = firstmap.getWidth();        Log.i("original width and height:", widthorig + "\n" + heightorig);        bt.setOnClickListener(new OnClickListener() {            @SuppressWarnings("unchecked")            public void onClick(View v) {                // TODO Auto-generated method stub                new MyAsyncTask().execute(filesPath);                i++;                scalex = 1;// 画图后初始化缩放比例                scaley = 1;                degrees=0;            }        });        bt2.setOnClickListener(new OnClickListener() {            public void onClick(View v) {                // TODO Auto-generated method stub                new MyScaleAsyncTask().execute();            }        });        bt3.setOnClickListener(new OnClickListener() {            public void onClick(View v) {                // TODO Auto-generated method stub                new MyRotateAsyncTask().execute(firstmap);                degrees=degrees+10;            }        });    }    private class MyRotateAsyncTask extends AsyncTask<Bitmap, Void, Bitmap> {        @Override        protected Bitmap doInBackground(Bitmap... params) {            // TODO Auto-generated method stub            Matrix matrix = new Matrix();            matrix.postRotate(degrees);            Bitmap bitmap = Bitmap.createBitmap(params[0], 0, 0, widthorig,                    heightorig, matrix, true);            return bitmap;        }        @Override        protected void onPostExecute(Bitmap result) {            // TODO Auto-generated method stub            super.onPostExecute(result);            imageView.setImageBitmap(result);        }    }    private class MyScaleAsyncTask extends AsyncTask<Bitmap, Void, Bitmap> {        @Override        protected Bitmap doInBackground(Bitmap... params) {            // TODO Auto-generated method stub            Matrix matrix = new Matrix();            scalex = (float) (scalex * 0.9);            scaley = (float) (scaley * 0.9);            matrix.postScale(scalex, scaley);            bitmap = Bitmap.createBitmap(                    BitmapFactory.decodeFile(filesPath.get(i)), 0, 0, 400, 600,                    matrix, true);            return bitmap;        }        @Override        protected void onPostExecute(Bitmap result) {            // TODO Auto-generated method stub            super.onPostExecute(result);            imageView.setImageBitmap(bitmap);        }    }    private class MyAsyncTask extends AsyncTask<List<String>, Void, Bitmap> {        Bitmap map;        @Override        protected void onPreExecute() {            // TODO Auto-generated method stub            super.onPreExecute();            dialog.show();        }        @Override        protected Bitmap doInBackground(List<String>... params) {            // TODO Auto-generated method stub            String path = params[0].get(i);            map = BitmapFactory.decodeFile(path);            return map;        }        @Override        protected void onPostExecute(Bitmap result) {            // TODO Auto-generated method stub            imageView.setImageBitmap(result);            firstmap = result;            super.onPostExecute(result);            dialog.dismiss();        }    }}

activity_main.xml

<RelativeLayout 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"    tools:context="${packageName}.${activityClass}" >    <Button        android:id="@+id/button1"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:layout_centerHorizontal="true"        android:text="切换图片" />    <ImageView        android:id="@+id/imageView1"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:layout_below="@+id/button1"        android:layout_centerHorizontal="true"        android:layout_marginTop="14dp"        android:src="@drawable/ic_launcher" />    <Button        android:id="@+id/button2"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:layout_alignParentLeft="true"        android:layout_alignParentTop="true"        android:layout_marginLeft="16dp"        android:text="缩小图片" />    <Button        android:id="@+id/button3"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:layout_above="@+id/imageView1"        android:layout_toRightOf="@+id/button1"        android:text="旋转图片" /></RelativeLayout>