我目前正在研究一個應用程序,在初始階段,我有一個錯誤,我不知道如何解決!我希望這個應用程序做的事情基本上是從我在資產文件夾(/app/src/main/assets/tvshows.xml)中創建的xml文件中檢索根節點,並使用TextView將其顯示在屏幕上!我得到一個空指針異常,並且應用程序保持「不幸停止」。如果你能爲我澄清這一點,我會非常感激。無法解決此nullPointerException,應用程序始終停止
import android.os.Bundle;
import android.support.v7.app.ActionBarActivity;
import android.widget.TextView;
import org.w3c.dom.Document;
import org.xml.sax.InputSource;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
public class MainActivity extends ActionBarActivity {
TextView printText;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Document xmlDoc = getDocument("/app/src/main/res/TvShows/tvshows.xml");
TextView printText = (TextView) findViewById(R.id.printText);
printText.setText(xmlDoc.getDocumentElement().getNodeName());
}
private Document getDocument(String domDoc) {
try {
DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
factory.setIgnoringComments(true);
factory.setIgnoringElementContentWhitespace(true);
factory.setValidating(true);
DocumentBuilder builder = factory.newDocumentBuilder();
AssetManager assetManager = this.getAssets();
InputStream is = assetManager.open("tvshows.xml");
InputSource inStream = new InputSource(is);
return builder.parse(inStream);
}
catch(Exception e) {
TextView printText = (TextView) findViewById(R.id.printText);
printText.setText(e.getMessage());
return null;
}
}
}
錯誤信息:
02-06 15:59:08.271 1973-1973/com.example.ashwinpraveen1.domdoc E/AndroidRuntime﹕ FATAL EXCEPTION: main
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.ashwinpraveen1.domdoc/com.example.ashwinpraveen1.domdoc.MainActivity}: java.lang.NullPointerException
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2223)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2273)
at android.app.ActivityThread.access$600(ActivityThread.java:144)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1259)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:137)
at android.app.ActivityThread.main(ActivityThread.java:5145)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:525)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.NullPointerException
at com.example.ashwinpraveen1.domdoc.MainActivity.onCreate(MainActivity.java:28)
at android.app.Activity.performCreate(Activity.java:5133)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2180)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2273)
at android.app.ActivityThread.access$600(ActivityThread.java:144)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1259)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:137)
at android.app.ActivityThread.main(ActivityThread.java:5145)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:525)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
at dalvik.system.NativeStart.main(Native Method)
後的錯誤消息。 – Simas 2015-02-06 09:42:57
@ user3249477是的,我很抱歉。 這些是錯誤信息: – 2015-02-06 09:49:19