Question

当我按下按钮时，我试图从数组中获取随机字符串。

到目前为止，它适用于在应用程序启动时获取随机字符串，但在启动后按下按钮无法使其工作。

编辑：它现在在启动时崩溃了吗？

我的新代码：

private String[] myString;
private static final Random rgenerator = new Random();


@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);



    TextView tv = (TextView) findViewById(R.id.joke);
  Resources res = getResources();

    myString = res.getStringArray(R.array.Jokes); 

    String q = myString[rgenerator.nextInt(myString.length)];    
    tv.setText(q);
    Button btn = (Button)findViewById(R.id.button);


 btn.setOnClickListener(new OnClickListener() { 
public void onClick(View v) {

    myString = res.getStringArray(R.array.Jokes); 

    String q = myString[rgenerator.nextInt(myString.length)];    
    tv.setText(q);
  }
});

}
}

Logcat说：

03-31 22:47:35.777: W/dalvikvm(1152): threadid=3: thread exiting with uncaught exception (group=0x4001b188)
03-31 22:47:35.777: E/AndroidRuntime(1152): Uncaught handler: thread main exiting due to uncaught exception
03-31 22:47:35.903: E/AndroidRuntime(1152): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.jc.dkjokes/com.jc.dkjokes.DanskeJokesMain}: java.lang.NullPointerException
03-31 22:47:35.903: E/AndroidRuntime(1152):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2417)
03-31 22:47:35.903: E/AndroidRuntime(1152):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2512)
03-31 22:47:35.903: E/AndroidRuntime(1152):     at android.app.ActivityThread.access$2200(ActivityThread.java:119)
03-31 22:47:35.903: E/AndroidRuntime(1152):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1863)
03-31 22:47:35.903: E/AndroidRuntime(1152):     at android.os.Handler.dispatchMessage(Handler.java:99)
03-31 22:47:35.903: E/AndroidRuntime(1152):     at android.os.Looper.loop(Looper.java:123)
03-31 22:47:35.903: E/AndroidRuntime(1152):     at android.app.ActivityThread.main(ActivityThread.java:4363)
03-31 22:47:35.903: E/AndroidRuntime(1152):     at java.lang.reflect.Method.invokeNative(Native Method)
03-31 22:47:35.903: E/AndroidRuntime(1152):     at java.lang.reflect.Method.invoke(Method.java:521)
03-31 22:47:35.903: E/AndroidRuntime(1152):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:860)
03-31 22:47:35.903: E/AndroidRuntime(1152):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:618)
03-31 22:47:35.903: E/AndroidRuntime(1152):     at dalvik.system.NativeStart.main(Native Method)
03-31 22:47:35.903: E/AndroidRuntime(1152): Caused by: java.lang.NullPointerException
03-31 22:47:35.903: E/AndroidRuntime(1152):     at android.app.Activity.findViewById(Activity.java:1612)
03-31 22:47:35.903: E/AndroidRuntime(1152):     at com.jc.dkjokes.DanskeJokesMain.<init>(DanskeJokesMain.java:17)
03-31 22:47:35.903: E/AndroidRuntime(1152):     at java.lang.Class.newInstanceImpl(Native Method)
03-31 22:47:35.903: E/AndroidRuntime(1152):     at java.lang.Class.newInstance(Class.java:1479)
03-31 22:47:35.903: E/AndroidRuntime(1152):     at android.app.Instrumentation.newActivity(Instrumentation.java:1021)
03-31 22:47:35.903: E/AndroidRuntime(1152):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2409)
03-31 22:47:35.903: E/AndroidRuntime(1152):     ... 11 more
03-31 22:47:35.963: I/dalvikvm(1152): threadid=7: reacting to signal 3
03-31 22:47:36.148: I/dalvikvm(1152): Wrote stack trace to '/data/anr/traces.txt'

SNOX

Answer 1

你必须定义onClickListener（）以在按钮点击时生成字符串，像这样，

    Button btn = (Button)findViewbyId(R.id.yourbuttonid);
    btn.setonclickListener(new onClickListner(){
          public void onclick()
          {
               //write your oncreate code here again
          }
    });

Answer 2

要实现这一点，您需要在main.xml文件中声明一个按钮，然后您必须在活动中初始化该按钮。然后，您必须在该按钮上设置单击事件侦听器。

<Button
    android:layout_width="fill_parent" 
    android:layout_height="wrap_content"
    android:id="@+id/buttonClick"
    />

<强>代码

TextView tv = (TextView) findViewById(R.id.joke);
Button btn = (Button)findViewbyId(R.id.buttonClick);
    btn.setonclickListener(new onClickListner(){
          public void onclick()
          {
               myString =  getResources().getStringArray(R.array.Jokes); 
               String q = myString[rgenerator.nextInt(myString.length)];
               tv.setText(q);
          }
    });

Answer 3

您尚未为onClickListener定义Button。请按以下步骤操作：

Button button = findViewById(R.id.button);
TextView tv = findViewById(R.id.joke);

button.setOnClickListener(new OnClickListener()  
    public void onClick(View view) {
        String[] myString = getResources().getStringArray(R.array.Jokes); 
        tv.setText(myString[rgenerator.nextInt(myString.length)]);
    }
});

按下按钮上的随机字符串

3 个答案: