实现查看网络图片功能

一、任务需求

二、任务实现

1  UI界面设计

2 代码实现

<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>

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();

4000
Message msg = new Message();
msg.what = ERROR;
handler.sendMessage(msg);
}
}
}.start();
}
}

}

附：Android 线程处理

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();
}
}

}
}