Question

我想掌握从url解析json内容所以我尝试了一个小练习。我创建了一个小应用程序。我的第一步是从网址获取内容。当应用程序“停止工作”时我卡住了，而logcat没有任何线索显示我错在哪里。

的活动：

包tri.jsonparser;

//import...

public class MainActivity extends Activity {

    URL url;
        HttpURLConnection conn;
    String str;
    Button btn;
    TextView content;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        // TODO Auto-generated method stub
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        btn = (Button) findViewById(R.id.button);
        content = (TextView) findViewById(R.id.textContent);

        btn.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View v) {
                // TODO Auto-generated method stub
                try {
                    url = new URL("http://thinktodo.net/LocationServiceSystem/index.php/location/getLocation?username=1");
                    conn = (HttpURLConnection) url.openConnection();
                    Log.d("my tag", "connection ok");
                    BufferedReader br = new BufferedReader(new InputStreamReader(conn.getInputStream()));
                    Log.d("my tag", "reader ok");
                    str = br.readLine();
                    content.setText(str);
                    br.close();
                } catch (IOException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
            }
        }); 
    }
}

activity_main.xml中：

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent" >

    <Button
        android:id="@+id/button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@+id/textViewLat"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="118dp"
        android:text="Get content" />

    <TextView
        android:id="@+id/textContent"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_alignParentLeft="true"
        android:layout_alignParentTop="true"
        android:layout_marginTop="58dp"
        android:text="Content"
        android:textAppearance="?android:attr/textAppearanceLarge" />

</RelativeLayout>

logcat的：

04-22 16:24:42.365: E/cutils-trace(1456): Error opening trace file: No such file or directory (2)
04-22 16:24:42.421: E/memtrack(1456): Couldn't load memtrack module (No such file or directory)
04-22 16:24:42.421: E/android.os.Debug(1456): failed to load memtrack module: -2
04-22 16:24:42.737: E/cutils-trace(1467): Error opening trace file: No such file or directory (2)
04-22 16:24:42.789: E/memtrack(1467): Couldn't load memtrack module (No such file or directory)
04-22 16:24:42.789: E/android.os.Debug(1467): failed to load memtrack module: -2
04-22 16:24:43.093: E/OpenGLRenderer(1478): Getting MAX_TEXTURE_SIZE from GradienCache
04-22 16:24:43.101: E/OpenGLRenderer(1478): MAX_TEXTURE_SIZE: 8192
04-22 16:24:43.145: E/OpenGLRenderer(1478): Getting MAX_TEXTURE_SIZE from Caches::initConstraints()
04-22 16:24:43.149: E/OpenGLRenderer(1478): MAX_TEXTURE_SIZE: 8192
04-22 16:24:45.297: E/AndroidRuntime(1478): FATAL EXCEPTION: main
04-22 16:24:45.297: E/AndroidRuntime(1478): Process: tri.jsonparser, PID: 1478
04-22 16:24:45.297: E/AndroidRuntime(1478): android.os.NetworkOnMainThreadException
04-22 16:24:45.297: E/AndroidRuntime(1478): at android.os.StrictMode$AndroidBlockGuardPolicy.onNetwork(StrictMode.java:1145)
04-22 16:24:45.297: E/AndroidRuntime(1478):     at java.net.InetAddress.lookupHostByName(InetAddress.java:385)
04-22 16:24:45.297: E/AndroidRuntime(1478): at java.net.InetAddress.getAllByNameImpl(InetAddress.java:236)
04-22 16:24:45.297: E/AndroidRuntime(1478): at java.net.InetAddress.getAllByName(InetAddress.java:214)
04-22 16:24:45.297: E/AndroidRuntime(1478): at com.android.okhttp.internal.Dns$1.getAllByName(Dns.java:28)
04-22 16:24:45.297: E/AndroidRuntime(1478): at com.android.okhttp.internal.http.RouteSelector.resetNextInetSocketAddress(RouteSelector.java:216)
04-22 16:24:45.297: E/AndroidRuntime(1478): at com.android.okhttp.internal.http.RouteSelector.next(RouteSelector.java:122)
04-22 16:24:45.297: E/AndroidRuntime(1478): at com.android.okhttp.internal.http.HttpEngine.connect(HttpEngine.java:292)
04-22 16:24:45.297: E/AndroidRuntime(1478): at com.android.okhttp.internal.http.HttpEngine.sendSocketRequest(HttpEngine.java:255)
04-22 16:24:45.297: E/AndroidRuntime(1478): at com.android.okhttp.internal.http.HttpEngine.sendRequest(HttpEngine.java:206)
04-22 16:24:45.297: E/AndroidRuntime(1478): at com.android.okhttp.internal.http.HttpURLConnectionImpl.execute(HttpURLConnectionImpl.java:345)
04-22 16:24:45.297: E/AndroidRuntime(1478): at com.android.okhttp.internal.http.HttpURLConnectionImpl.getResponse(HttpURLConnectionImpl.java:296)
04-22 16:24:45.297: E/AndroidRuntime(1478): at com.android.okhttp.internal.http.HttpURLConnectionImpl.getInputStream(HttpURLConnectionImpl.java:179)
04-22 16:24:45.297: E/AndroidRuntime(1478): at tri.jsonparser.MainActivity$1.onClick(MainActivity.java:41)
04-22 16:24:45.297: E/AndroidRuntime(1478): at android.view.View.performClick(View.java:4438)
04-22 16:24:45.297: E/AndroidRuntime(1478): at android.view.View$PerformClick.run(View.java:18422)
04-22 16:24:45.297: E/AndroidRuntime(1478): at android.os.Handler.handleCallback(Handler.java:733)
04-22 16:24:45.297: E/AndroidRuntime(1478): at android.os.Handler.dispatchMessage(Handler.java:95)
04-22 16:24:45.297: E/AndroidRuntime(1478): at android.os.Looper.loop(Looper.java:136)
04-22 16:24:45.297: E/AndroidRuntime(1478): at android.app.ActivityThread.main(ActivityThread.java:5017)
04-22 16:24:45.297: E/AndroidRuntime(1478): at java.lang.reflect.Method.invokeNative(Native Method)
04-22 16:24:45.297: E/AndroidRuntime(1478): at java.lang.reflect.Method.invoke(Method.java:515)
04-22 16:24:45.297: E/AndroidRuntime(1478): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
04-22 16:24:45.297: E/AndroidRuntime(1478): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
04-22 16:24:45.297: E/AndroidRuntime(1478): at dalvik.system.NativeStart.main(Native Method)
04-22 16:24:48.121: E/InputDispatcher(547): channel '52a395b4 tri.jsonparser/tri.jsonparser.MainActivity (server)' ~ Channel is unrecoverably broken and will be disposed!

Answer 1

您需要在Runnable中实现连接并在另一个线程上运行它。这是因为Android不允许您在UI线程上执行网络请求（这是您在活动中默认使用的）。 Android执行此操作，因为您的网络请求可能需要很长时间才能返回，并且UI线程的执行在此之前停止（“阻止”）。尝试使用下面的代码替换你的btn.setOnClickListener（）。

    btn.setOnClickListener(new OnClickListener() {

          @Override
          public void onClick(View v) {
            // TODO Auto-generated method stub
                Runnable r = new Runnable(){
                @Override
                public void run(){
            try {
                url = new URL("http://thinktodo.net/LocationServiceSystem/index.php/location/getLocation?username=1");
                conn = (HttpURLConnection) url.openConnection();
                Log.d("my tag", "connection ok");
                BufferedReader br = new BufferedReader(new InputStreamReader(conn.getInputStream()));
                Log.d("my tag", "reader ok");
                str = br.readLine();
                Runnable uir = new Runnable(){
                 @Override
                 public void run()
                 {
                    content.setText(str);
                 }
                };
                MainActivity.this.runOnUiThread(uir);
                br.close();
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }
        };
        Thread th = new Thread(r);
        th.start();
        }
    });

一旦您的请求与服务器建立连接，TextView的内容就会发生变化。编辑：正如@ njzk2指出的那样，设置TextView的内容必须在UI线程上进行。

从URL读取内容时出错 - 无法从logcat中找到任何线索

1 个答案: