Android意向返回Nullpointerexception
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我希望获得有关如何在传递意图时解决NullPointerException问题的指导。我想创建一个列表视图，可以在其中单击以显示一些相关信息。因此，基本上，主列表可以运行，但是当我单击该条目时，它就会崩溃。
我已经检查过LogCat，它说我有Nullpointerexception，我不熟悉如何检查/查找Null变量。我认为我的mRowId为null，但我不知道如何使其成为已定义的值。
有人可以帮我发现下面的意图问题吗？
传递意图的主要文件是这个。
@Override
public void onListItemClick(ListView l, View v, int position, long id) {
super.onListItemClick(l, v, position, id);
Intent i = new Intent(this, drugdetail.class);
i.putExtra(DrugsDbAdapter.KEY_ROWID, id);
startActivity(i);
}
package com.paad.medboxsd;
public class drugdetail extends Activity{
private TextView mDrugText;
private TextView mContentText;
private Long mRowId;
DrugsDbAdapter.DatabaseHelper mDbHelper = new DrugsDbAdapter.DatabaseHelper(this);
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.drug_info);
mDrugText = (TextView) findViewById(R.id.drug);
mContentText = (TextView) findViewById(R.id.content);
//potentially where the problem on Nullpointers lie where LogCat says null pointer exception from fetchDrugs(). Meaning likely that mRowId is Null.
//mRowId = savedInstanceState != null ? savedInstanceState.getLong(DrugsDbAdapter.KEY_ROWID) : null;
Bundle extras = getIntent().getExtras();
mRowId = extras.getLong(DrugsDbAdapter.KEY_ROWID);
Cursor drug = mDbHelper.fetchDrug(mRowId);
//Managing Cursor to pluck values to display
startManagingCursor(drug);
mDrugText.setText(drug.getString(drug.getColumnIndexOrThrow(DrugsDbAdapter.KEY_DRUG)));
mContentText.setText(drug.getString(drug.getColumnIndexOrThrow(DrugsDbAdapter.KEY_CONTENT)));
}
05-26 15:27:48.698: ERROR/AndroidRuntime(4829): FATAL EXCEPTION: main
05-26 15:27:48.698: ERROR/AndroidRuntime(4829): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.paad.medboxsd/com.paad.medboxsd.drugdetail}: java.lang.NullPointerException
05-26 15:27:48.698: ERROR/AndroidRuntime(4829): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2663)
05-26 15:27:48.698: ERROR/AndroidRuntime(4829): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2679)
05-26 15:27:48.698: ERROR/AndroidRuntime(4829): at android.app.ActivityThread.access$2300(ActivityThread.java:125)
05-26 15:27:48.698: ERROR/AndroidRuntime(4829): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2033)
05-26 15:27:48.698: ERROR/AndroidRuntime(4829): at android.os.Handler.dispatchMessage(Handler.java:99)
05-26 15:27:48.698: ERROR/AndroidRuntime(4829): at android.os.Looper.loop(Looper.java:123)
05-26 15:27:48.698: ERROR/AndroidRuntime(4829): at android.app.ActivityThread.main(ActivityThread.java:4627)
05-26 15:27:48.698: ERROR/AndroidRuntime(4829): at java.lang.reflect.Method.invokeNative(Native Method)
05-26 15:27:48.698: ERROR/AndroidRuntime(4829): at java.lang.reflect.Method.invoke(Method.java:521)
05-26 15:27:48.698: ERROR/AndroidRuntime(4829): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
05-26 15:27:48.698: ERROR/AndroidRuntime(4829): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
05-26 15:27:48.698: ERROR/AndroidRuntime(4829): at dalvik.system.NativeStart.main(Native Method)
05-26 15:27:48.698: ERROR/AndroidRuntime(4829): Caused by: java.lang.NullPointerException
05-26 15:27:48.698: ERROR/AndroidRuntime(4829): at com.paad.medboxsd.DrugsDbAdapter$DatabaseHelper.fetchDrug(DrugsDbAdapter.java:195)
05-26 15:27:48.698: ERROR/AndroidRuntime(4829): at com.paad.medboxsd.drugdetail.onCreate(drugdetail.java:35)
05-26 15:27:48.698: ERROR/AndroidRuntime(4829): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
05-26 15:27:48.698: ERROR/AndroidRuntime(4829): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2627)
05-26 15:27:48.698: ERROR/AndroidRuntime(4829): ... 11 more
没有找到相关结果
已邀请:
1 个回复
葛瞎说漓
但是您立即在这里再次设置Bundle extras = getIntent().getExtras(); mRowId = extras.getLong(DrugsDbAdapter.KEY_ROWID);mRowId = (savedInstanceState != null) ? savedInstanceState.getLong(DrugsDbAdapter.KEY_ROWID) : null; if (mRowId == null) { Bundle extras = getIntent().getExtras(); mRowId = (extras != null) ? extras.getLong(DrugsDbAdapter.KEY_ROWID) : null; } if (mRowId != null) { //database stuff here } else { //error handling here }