Android 应用中 setText 上的空对象引用 [英] Null object reference on setText in Android app

问题描述

我的应用程序在此 setText 此处崩溃.我想可能是因为它找不到 id，所以我查看了 R.java 并在那里找到了 id.我很困惑为什么它仍然崩溃.

My app crashes on this setText here. I think probably because it cannot find the id so I looked into to R.java and found the id there. I'm confused why it still crashes.

TextView city = (TextView)findViewById(R.id.city_result);
city.setText(msg[0]);

R.java

public static final int city_result=0x7f080041;

并且这段代码在public static final class id方法中.

and this code is in the public static final class id method.

任何帮助将不胜感激！谢谢！！

Any help will be appreciated! Thanks!!

================更多代码:

================ More Code:

 protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_weather_report);
    if (savedInstanceState == null) {
        getSupportFragmentManager().beginTransaction()
                .add(R.id.container, new PlaceholderFragment())
                .commit();
    }

    //get message from intent
    Intent intent = getIntent();
    String[] message = intent.getStringArrayExtra(MainActivity.EXTRA_MESSAGE);
    setResult(message);
}
public void setResult(String[] msg)
    {
        //test
        TextView city = (TextView)findViewById(R.id.city_result);
        city.setText(msg[0]);
    }

这个文件我刚开始，其他地方只是系统生成的新文件代码，我还没有编辑.这是 logcat:

This file I just started, elsewhere is just system generated new file code, I didn't edit yet. Here's logcat:

    java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.chen.weather/com.example.chen.weather.WeatherReport}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setText(java.lang.CharSequence)' on a null object reference
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2298)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2360)
            at android.app.ActivityThread.access$800(ActivityThread.java:144)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1278)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:135)
            at android.app.ActivityThread.main(ActivityThread.java:5221)
            at java.lang.reflect.Method.invoke(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:372)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
     Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setText(java.lang.CharSequence)' on a null object reference
            at com.example.chen.weather.WeatherReport.setResult(WeatherReport.java:78)
            at com.example.chen.weather.WeatherReport.onCreate(WeatherReport.java:32)
            at android.app.Activity.performCreate(Activity.java:5933)
            at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1105)
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2251)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2360)
                at android.app.ActivityThread.access$800(ActivityThread.java:144)
                at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1278)
                at android.os.Handler.dispatchMessage(Handler.java:102)
                at android.os.Looper.loop(Looper.java:135)
                at android.app.ActivityThread.main(ActivityThread.java:5221)
                at java.lang.reflect.Method.invoke(Native Method)
                at java.lang.reflect.Method.invoke(Method.java:372)
                at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)
                at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)

推荐答案

NullPointerException: 尝试调用虚方法 'voidandroid.widget.TextView.setText

NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setText

表示 city TextView 对象为 null 由于:

Means city TextView object is null due to :

1. setContentView 在使用 findViewById 之前不会被调用:

1. setContentView is not called before using findViewById:

2. 不使用 TextView 定义为 city_result id 的布局.确保在 setContentView

2. Not using layout in which TextView is defined with city_result id. make sure you are passing right layout in setContentView

这篇关于Android 应用中 setText 上的空对象引用的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！