实现查看网络图片功能



一、任务需求

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在EditText中输入网络图片的地址，点击“浏览”按钮在上方显示网络中的图片。

二、任务实现

1  UI界面设计

2 代码实现

activity_main

<LinearLayout 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"    android:orientation="vertical"    tools:context=".MainActivity" >    <ImageView        android:id="@+id/iv"        android:layout_width="fill_parent"        android:layout_height="fill_parent"        android:layout_weight="1" />    <EditText        android:id="@+id/et_path"        android:layout_width="fill_parent"        android:layout_height="wrap_content"        android:hint="请输入图片路径"        android:text="@string/address"        android:maxLines="1" />    <Button        android:layout_width="fill_parent"        android:layout_height="wrap_content"        android:onClick="click"        android:text="浏览" /></LinearLayout>

MainActivity.java

public class MainActivity extends AppCompatActivity {    protected static final int CHANGE_UI = 1;    protected static final int ERROR = 2;    private EditText et_path;    private ImageView iv;    // 主线程创建消息处理器    private Handler handler = new Handler(){        public void handleMessage(android.os.Message msg) {            if(msg.what == CHANGE_UI){                Bitmap bitmap = (Bitmap) msg.obj;                iv.setImageBitmap(bitmap);            }else if(msg.what == ERROR){                Toast.makeText(MainActivity.this, "显示图片错误", Toast.LENGTH_SHORT).show();            }        };    };    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        et_path = (EditText) findViewById(R.id.et_path);        iv = (ImageView) findViewById(R.id.iv);    }    public void click(View view) {        final String path = et_path.getText().toString().trim();        if (TextUtils.isEmpty(path)) {            Toast.makeText(this, "图片路径不能为空", Toast.LENGTH_SHORT).show();        } else {            //子线程请求网络,Android4.0以后访问网络不能放在主线程中            new Thread() { //创建一个新的线程  new Runnable()可以省略                public void run() {                    // 连接服务器 get 请求 获取图片.                    try {                        URL url = new URL(path);       //创建URL对象                        // 根据url 发送 http的请求.                        HttpURLConnection conn = (HttpURLConnection) url                                .openConnection();                        // 设置请求的方式                        conn.setRequestMethod("GET");                        //设置超时时间                        conn.setConnectTimeout(5000);                        // 得到服务器返回的响应码                        int code = conn.getResponseCode();                        //请求网络成功后返回码是200                        if (code == 200) {                            //获取输入流                            InputStream is = conn.getInputStream();                            //将流转换成Bitmap对象                            Bitmap bitmap = BitmapFactory.decodeStream(is);                            //iv.setImageBitmap(bitmap);                            //TODO: 告诉主线程一个消息:帮我更改界面。内容:bitmap                            Message msg = new Message();                            msg.what = CHANGE_UI;                            msg.obj = bitmap;                            handler.sendMessage(msg);                        } else {                            //返回码不是200  请求服务器失败                            Message msg = new Message();                            msg.what = ERROR;                            handler.sendMessage(msg);                        }                    } catch (Exception e) {                        e.printStackTrace();                        Message msg = new Message();                        msg.what = ERROR;                        handler.sendMessage(msg);                    }                }            }.start();        }    }}

附：Android 线程处理

有关Android线程处理机制可通过以下代码实现三种线程处理形式：

import java.util.Date;public class ThreadClassDemo {    public static void main(String[] args) {        // TODO Auto-generated method stub        ClockThread clockThread = new ClockThread();//      clockThread.start();        //  Thread thread = new Thread(clockThread);        //thread.start();    new Thread(new Runnable(){        @Override        public void run(){            while (true){                System.out.println(new Date());                try {                    Thread.sleep(1000);                } catch (InterruptedException e) {                    // TODO Auto-generated catch block                    e.printStackTrace();                }            }        }    }).start();        System.out.println("main");    }}class ClockThread implements Runnable{ //extend Thread    @Override    public void run(){        //super.run();        while(true){            System.out.println(new Date());            try {                Thread.sleep(1000);            } catch (InterruptedException e) {                // TODO Auto-generated catch block                e.printStackTrace();            }        }    }}