Question

所以我想从字符串中提取几个字符然后在Textview上显示它，如下所示：

  Uri uri = Uri.parse("content://sms/inbox");
  Cursor crsr = getContentResolver().query(uri, null, null, null, null);

  startManagingCursor(crsr);

  String[] columns = new String[] { "address", "person", "date", "body",
      "type" };

  String address = "";
  String msg = "";

  ArrayList<String> conversations = new ArrayList<String>();

  if (crsr.getCount() > 0) {
    while (crsr.moveToNext()) {
      address = crsr.getString(crsr.getColumnIndex(columns[0]));
      msg = crsr.getString(crsr.getColumnIndex(columns[3]));
      msg = msg.substring(1, 30) + "..."; // THIS CAUSES FATAL ERROR          
      conversations.add(address + "\n\n" + msg);          
    }
  }

使用substring非常简单，但我无法理解为什么它会给出错误并显示致命错误，这里是跟踪：

E/AndroidRuntime(14023):  FATAL EXCEPTION: main
E/AndroidRuntime(14023):  java.lang.RuntimeException: Unable to start activity......
E/AndroidRuntime(14023):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2313)
E/AndroidRuntime(14023):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2365)
E/AndroidRuntime(14023):    at android.app.ActivityThread.access$600(ActivityThread.java:156)
E/AndroidRuntime(14023):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344)
E/AndroidRuntime(14023):    at android.os.Handler.dispatchMessage(Handler.java:99)
E/AndroidRuntime(14023):    at android.os.Looper.loop(Looper.java:153)
E/AndroidRuntime(14023):    at android.app.ActivityThread.main(ActivityThread.java:5336)
E/AndroidRuntime(14023):    at java.lang.reflect.Method.invokeNative(Native Method)
E/AndroidRuntime(14023):    at java.lang.reflect.Method.invoke(Method.java:511)
E/AndroidRuntime(14023):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:833)
E/AndroidRuntime(14023):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:600)
E/AndroidRuntime(14023):    at de.robv.android.xposed.XposedBridge.main(XposedBridge.java:112)
E/AndroidRuntime(14023):    at dalvik.system.NativeStart.main(Native Method)
E/AndroidRuntime(14023):  Caused by: java.lang.StringIndexOutOfBoundsException: length=8; regionStart=1; regionLength=29
E/AndroidRuntime(14023):    at java.lang.String.startEndAndLength(String.java:583)
E/AndroidRuntime(14023):    at java.lang.String.substring(String.java:1464)
E/AndroidRuntime(14023):    at com.sarfraznawaz.cleansms.MainActivity.onCreate(MainActivity.java:41)
E/AndroidRuntime(14023):    at android.app.Activity.performCreate(Activity.java:5122)
E/AndroidRuntime(14023):    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1081)
E/AndroidRuntime(14023):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2277)

有人能说出这条线有什么问题吗？

msg = msg.substring(1, 30) + "...";

由于

Answer 1

您的消息msg不是那么长（少于30个字符长）。这就是问题所在。

Answer 2

从日志中明确提到，您的字符串长度不是30 。

因此，在使用subString之前，请检查其长度。

 if(msg.length()>=30)
 msg = msg.substring(1, 30) + "..."; 
 else 
 msg = msg.substring(1, msg.length()) + "...";   // Also check here string length is more than 1

java substring引发异常

2 个答案: