Question

在这里练习基本的android示例我在我的代码中得到空指针异常如何解决这个问题。在这里附上代码。

public void onClick(View v) {

        switch (v.getId()) {
        case R.id.toggleButton1:

            // TODO Auto-generated method stub
            try {
                if (t1.isChecked()) {
                    StringBuilder s1 = new StringBuilder();
                    s1.append(b1.getText());
                    Toast.makeText(getBaseContext(), s1.toString(),
                            Toast.LENGTH_SHORT);

                } else {

                    TextView t1 = (TextView) findViewById(R.id.t1);
                    StringBuilder s2 = new StringBuilder();
                    s2.append(t1.getText());
                    Toast.makeText(getBaseContext(), t1.toString(),
                            Toast.LENGTH_SHORT);
                }
            } catch (Exception e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        case R.id.button1:
            try {
                Intent browserIntent = new Intent(Intent.ACTION_VIEW,
                        Uri.parse("http://www.mkyong.com"));
                startActivity(browserIntent);
            } catch (Exception e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }

不知道问题出在哪一行，这里附加堆栈跟踪

    07-06 05:56:54.373: D/AndroidRuntime(940): Shutting down VM
07-06 05:56:54.373: W/dalvikvm(940): threadid=1: thread exiting with uncaught exception (group=0x409961f8)
07-06 05:56:54.393: E/AndroidRuntime(940): FATAL EXCEPTION: main
07-06 05:56:54.393: E/AndroidRuntime(940): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.xxx/com.example.xxx.MainActivity}: java.lang.NullPointerException
07-06 05:56:54.393: E/AndroidRuntime(940):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1955)
07-06 05:56:54.393: E/AndroidRuntime(940):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1980)
07-06 05:56:54.393: E/AndroidRuntime(940):  at android.app.ActivityThread.access$600(ActivityThread.java:122)
07-06 05:56:54.393: E/AndroidRuntime(940):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1146)
07-06 05:56:54.393: E/AndroidRuntime(940):  at android.os.Handler.dispatchMessage(Handler.java:99)
07-06 05:56:54.393: E/AndroidRuntime(940):  at android.os.Looper.loop(Looper.java:137)
07-06 05:56:54.393: E/AndroidRuntime(940):  at android.app.ActivityThread.main(ActivityThread.java:4340)
07-06 05:56:54.393: E/AndroidRuntime(940):  at java.lang.reflect.Method.invokeNative(Native Method)
07-06 05:56:54.393: E/AndroidRuntime(940):  at java.lang.reflect.Method.invoke(Method.java:511)
07-06 05:56:54.393: E/AndroidRuntime(940):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
07-06 05:56:54.393: E/AndroidRuntime(940):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
07-06 05:56:54.393: E/AndroidRuntime(940):  at dalvik.system.NativeStart.main(Native Method)
07-06 05:56:54.393: E/AndroidRuntime(940): Caused by: java.lang.NullPointerException
07-06 05:56:54.393: E/AndroidRuntime(940):  at com.example.xxx.MainActivity.onCreate(MainActivity.java:26)
07-06 05:56:54.393: E/AndroidRuntime(940):  at android.app.Activity.performCreate(Activity.java:4465)
07-06 05:56:54.393: E/AndroidRuntime(940):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1049)
07-06 05:56:54.393: E/AndroidRuntime(940):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1919)
07-06 05:56:54.393: E/AndroidRuntime(940):  ... 11 more
07-06 06:01:54.493: I/Process(940): Sending signal. PID: 940 SIG: 9

Answer 1

如果这是第26行（我无法确定 - 你遗漏了行号）：

case R.id.button1:

然后你需要在你的代码中指出它 - 例如像这样：

butt = (Button) findViewById(R.id.button1);
case butt:

我建议您查看其他示例程序来帮助您。

祝你好运！

如何在android中修复空指针异常

1 个答案: