Android之简单了解Bitmap显示图片及缓存图片

             1 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
 2     xmlns:tools="http://schemas.android.com/tools"
 3     android:layout_width="match_parent"
 4     android:layout_height="match_parent"
 5     android:orientation="vertical"
 6     tools:context="com.example.imagelook.MainActivity" >
 7 8     <EditText
 9         android:id="@+id/et_path"
10         android:layout_width="match_parent"
11         android:layout_height="wrap_content"
12         android:hint="@string/editText" >
13     </EditText>
1415     <Button
16         android:id="@+id/button1"
17         android:layout_width="wrap_content"
18         android:layout_height="wrap_content"
19         android:onClick="click"
20         android:text="@string/btn" />
2122     <ImageView
23         android:id="@+id/iv"
24         android:layout_width="wrap_content"
25         android:layout_height="wrap_content"/>
2627 </LinearLayout>

            package
             com.example.imagelook;


            import
             java.io.File;

            import
             java.io.FileOutputStream;

            import
             java.io.IOException;

            import
             java.io.InputStream;

            import
             java.net.HttpURLConnection;

            import
             java.net.URL;


            import
             android.app.Activity;

            import
             android.graphics.Bitmap;

            import
             android.graphics.BitmapFactory;

            import
             android.os.Bundle;

            import
             android.os.Handler;

            import
             android.os.Message;

            import
             android.util.Base64;

            import
             android.view.View;

            import
             android.widget.EditText;

            import
             android.widget.ImageView;



            public
            class MainActivity extends Activity {
    
    private EditText et_path;
    private ImageView iv;
    
    private Handler handler = new Handler(){
        //处理消息publicvoid handleMessage(Message msg) {
            
            Bitmap bitmap = (Bitmap) msg.obj;
            iv.setImageBitmap(bitmap);
        };
    };
    @Override
    protectedvoid onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        
        //1、找控件
        et_path = (EditText) findViewById(R.id.et_path);
        iv = (ImageView) findViewById(R.id.iv);
        
    }
    
    //2、点击按钮进行查看指定路径的源码publicvoid click(View v) throws IOException {
        
        new Thread(){
            publicvoid run(){
                try {
                    //2.1、获取访问图片的路径
                    String path = et_path.getText().toString().trim();
                    
                    File file = new File(getCacheDir(),Base64.encodeToString(path.getBytes(), Base64.DEFAULT));//test.png
                    if( file.exists() && file.length()>0 ) {
                        //使用缓存的图片
                        System.out.println("使用缓存图片");
                        Bitmap cacheBitmap = BitmapFactory.decodeFile(file.getAbsolutePath());
                        //把cacheBitmap显示到iv上
                        Message msg = Message.obtain();
                        msg.obj = cacheBitmap ;
                        handler.sendMessage(msg);
                        
                    }else{
                        //第一次访问 联网缓存图片
                        System.out.println("第一次访问连接网络");
                            
                        
                        //2.2 创建URL对象
                        URL url = new URL(path);
                        
                        //2.3 获取httpURLConnection
                        HttpURLConnection conn = (HttpURLConnection) url.openConnection();
                        
                        //2.4 设置请求方式
                        conn.setRequestMethod("GET");
                        
                        //2.5设置超时时间
                        conn.setConnectTimeout(5000);
                        
                        //2.6获取服务器状态码int code = conn.getResponseCode();
                        if (code == 200){
                            //2.7 获取图片数据 不管是什么数据（text 图片）都是以流行式返回
                            InputStream in = conn.getInputStream();
                            
                            //2.7缓存图片 谷歌提供一个缓存目录
                            FileOutputStream fos =  new FileOutputStream(file);
                            int len = -1 ;
                            byte[] buffer = newbyte[1024];//1kbwhile((len = in.read(buffer)) != -1){
                                fos.write(buffer,0,len);
                            }
                            fos.close();
                            in.close();
                            
                            //2.8 通过位图工厂获取bitmap
                            //Bitmap bitmap = BitmapFactory.decodeStream(in);
                            Bitmap bitmap = BitmapFactory.decodeFile(file.getAbsolutePath());//读取缓存
                            
                            //2.9 把bitmap 显示到iv上
                            Message msg = Message.obtain();//消息池有消息池拿数据，没有new一个
                            msg.obj = bitmap ;
                            handler.sendMessage(msg);//发消息                            
                        }
                
                    }
                } catch (Exception e) {
                    e.printStackTrace();
                }
            };
        }.start();
        
    }

}