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我已经编写了一个 Android 应用程序，用于检查与 Google 的 Internet 连接（我猜是通过套接字）！当我从我的网络线程（检查方法）得到答案时，我尝试用 setText 更新我的文本视图，但我得到一个空指针异常！这可能是我的代码中一个安静的简单错误，但我根本不明白。

这是我的主要活动：

package at.springsits.michi.hostchecker;

import android.os.Bundle;
import android.app.Activity;
import android.util.Log;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.TextView;

public class Main extends Activity implements OnClickListener {

    TextView connection_internet;
    Button pingbutton;
    Networking net;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        connection_internet = (TextView) findViewById(R.id.connection);
        pingbutton = (Button) findViewById(R.id.ping_button);
        pingbutton.setOnClickListener(this);
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }

    @Override
    public void onClick(View v) {
        new Thread(new Runnable() {
            public void run() {
            `enter code here`net.connectionToGoogle = Networking.testPingToGoogle();
                runOnUiThread(new Runnable() {
                    public void run() {
                        connection_internet.setText(String
                                .valueOf(net.connectionToGoogle));
                    }
                });
            }
        }).start();

    }

}

日志猫：

06-26 16:38:00.030: D/libEGL(2756): loaded /system/lib/egl/libEGL_adreno200.so
06-26 16:38:00.030: D/libEGL(2756): loaded /system/lib/egl/libGLESv1_CM_adreno200.so
06-26 16:38:00.030: D/libEGL(2756): loaded /system/lib/egl/libGLESv2_adreno200.so
06-26 16:38:00.030: I/Adreno200-EGL(2756): <eglInitialize:269>: EGL 1.4 QUALCOMM build: Nondeterministic AU_full_mako_PARTNER-ANDROID/JB-MR1-DEV_CL2961380_release_AU (CL2961380)
06-26 16:38:00.030: I/Adreno200-EGL(2756): Build Date: 12/10/12 Mon
06-26 16:38:00.030: I/Adreno200-EGL(2756): Local Branch: 
06-26 16:38:00.030: I/Adreno200-EGL(2756): Remote Branch: m/partner-android/jb-mr1-dev
06-26 16:38:00.030: I/Adreno200-EGL(2756): Local Patches: NONE
06-26 16:38:00.030: I/Adreno200-EGL(2756): Reconstruct Branch: NOTHING
06-26 16:38:00.070: D/OpenGLRenderer(2756): Enabling debug mode 0
06-26 16:38:03.414: W/dalvikvm(2756): threadid=11: thread exiting with uncaught exception (group=0x40bf9930)
06-26 16:38:03.414: E/AndroidRuntime(2756): FATAL EXCEPTION: Thread-6549
06-26 16:38:03.414: E/AndroidRuntime(2756): java.lang.NullPointerException
06-26 16:38:03.414: E/AndroidRuntime(2756):     at at.springsits.michi.hostchecker.Main$1.run(Main.java:37)
06-26 16:38:03.414: E/AndroidRuntime(2756):     at java.lang.Thread.run(Thread.java:856)
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1 回答 1

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net一片空白。您正试图在实例化之前访问其字段之一。

你在这里声明它：

Networking net

然后尝试在onClick()

net.connectionToGoogle = Networking.testPingToGoogle()

但现阶段net是null。onCreate()在您尝试使用它之前在您的或类似的实例中实例化它：

net = new Networking();
于 2013-06-26T14:43:46.533 回答