图片的旋转

主要运用了Matrix类，postRotate()方法和postScale()方法；

Matrix：中文是矩阵的意思，主要用于图片的缩放，平移与旋转；

postRotate()用于旋转，postScale()用于缩放；

具体MianAvtivity代码如下：

 1 package com.example.lenovo.a1105;
 2 
 3 import android.graphics.Bitmap;
 4 import android.graphics.BitmapFactory;
 5 import android.graphics.Matrix;
 6 import android.graphics.drawable.BitmapDrawable;
 7 import android.support.v7.app.AppCompatActivity;
 8 import android.os.Bundle;
 9 import android.view.Menu;
10 import android.view.MenuItem;
11 import android.view.View;
12 import android.widget.Button;
13 import android.widget.ImageView;
14 
15 public class MainActivity extends AppCompatActivity {
16 
17     private Bitmap myBitmap;
18     private Matrix myMatrix=new Matrix();
19     private int width;
20     private int height;
21     @Override
22     protected void onCreate(Bundle savedInstanceState) {
23         super.onCreate(savedInstanceState);
24         setContentView(R.layout.activity_main);
25 
26         Button rotaToLeft=(Button)findViewById(R.id.rotaToLeft);
27         Button rotaToRight=(Button)findViewById(R.id.rotaToRight);
28         Button scaleBig=(Button)findViewById(R.id.scaleBig);
29         Button scaleSmall=(Button)findViewById(R.id.scaleSmall);
30 
31         myBitmap= BitmapFactory.decodeResource(getResources(),R.drawable.pic);
32                                      //获取资源图片pic的Bitmap
33         width=myBitmap.getWidth();
34         height=myBitmap.getHeight();
35                             //这两句是获取图片原始大小
36 
37         //以下是四个按钮的单击事件
38 
39         rotaToLeft.setOnClickListener(new View.OnClickListener() {
40             @Override
41             public void onClick(View v) {
42                 myMatrix.postRotate(-90);  //逆时针旋转90°
43 
44                 Bitmap newBitmap=Bitmap.createBitmap(myBitmap,0,0,width,height,myMatrix,false);
45                                 //创建一个新的图片，重新绘图
46                 BitmapDrawable newBmp=new BitmapDrawable(newBitmap);
47                                //把Bitmap装换成Drawable，使其可以显示在ImageView与ImageButton中
48                 ImageView imageView=(ImageView)findViewById(R.id.pic);
49                                //创建Image对象
50                 imageView.setImageDrawable(newBmp);
51             }
52         });
53         rotaToRight.setOnClickListener(new View.OnClickListener() {
54             @Override
55             public void onClick(View v) {
56                 myMatrix.postRotate(90); //顺时针旋转90°
57                 Bitmap newBitmap=Bitmap.createBitmap(myBitmap,0,0,width,height,myMatrix,false);
58                 BitmapDrawable newBmp=new BitmapDrawable(newBitmap);
59                 ImageView imageView=(ImageView)findViewById(R.id.pic);
60                 imageView.setImageDrawable(newBmp);
61             }
62         });
63         scaleBig.setOnClickListener(new View.OnClickListener() {
64             @Override
65             public void onClick(View v) {
66                 myMatrix.postScale(1.2f, 1.2f);
67 
68                 Bitmap newBitmap=Bitmap.createBitmap(myBitmap,0,0,width,height,myMatrix,true);
69                 BitmapDrawable newBmp=new BitmapDrawable(newBitmap);
70                 ImageView imageView=(ImageView)findViewById(R.id.pic);
71                 imageView.setImageDrawable(newBmp);
72 
73             }
74         });
75         scaleSmall.setOnClickListener(new View.OnClickListener() {
76             @Override
77             public void onClick(View v) {
78                 myMatrix.postScale(0.5f, 0.5f);
79 
80                 Bitmap newBitmap=Bitmap.createBitmap(myBitmap,0,0,width,height,myMatrix,true);
81                 BitmapDrawable newBmp=new BitmapDrawable(newBitmap);
82                 ImageView imageView=(ImageView)findViewById(R.id.pic);
83                 imageView.setImageDrawable(newBmp);
84             }
85         });
86     }
87 
88 }

View Code

main.xml代码如下：

 1 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
 2     android:layout_width="match_parent"
 3     android:layout_height="match_parent"
 4     android:orientation="vertical">
 5 
 6     <ImageView
 7         android:id="@+id/pic"
 8         android:layout_width="wrap_content"
 9         android:layout_height="wrap_content"
10         android:layout_gravity="center"
11         android:background="@drawable/pic"
12         android:layout_marginTop="40dp"
13         />
14 
15     <LinearLayout
16         android:layout_width="wrap_content"
17         android:layout_height="wrap_content"
18         android:layout_marginTop="40dp"
19         android:orientation="horizontal">
20         <Button
21             android:id="@+id/rotaToLeft"
22             android:layout_width="wrap_content"
23             android:layout_height="wrap_content"
24             android:text="左旋" />
25         <Button
26             android:id="@+id/rotaToRight"
27             android:layout_width="wrap_content"
28             android:layout_height="wrap_content"
29             android:text="右旋" />
30 
31         <Button
32             android:id="@+id/scaleBig"
33             android:layout_width="wrap_content"
34             android:layout_height="wrap_content"
35             android:text="放大" />
36 
37         <Button
38             android:id="@+id/scaleSmall"
39             android:layout_width="wrap_content"
40             android:layout_height="wrap_content"
41             android:text="缩小" />
42 
43 
44     </LinearLayout>
45 
46 
47 </LinearLayout>