Question

当我单击应用程序上的按钮时，我在日志中收到上述错误。我将发布发送活动和接收活动的代码。

发送活动：

private TrackerDAO dbHelper;
private SimpleCursorAdapter dataAdapter;

String historyString = "";
long idDB;

long getlastID;
String getAD;
String Check;


public static long TripID;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_history_list);

    try{

    dbHelper = new TrackerDAO(this);

    }catch(SQLException e){

        e.printStackTrace();
    }

    dbHelper.open();

    displayListView();
}


private void displayListView() {

    Cursor cursor = dbHelper.fetchAllEntries();

    // The desired columns to be bound
    String[] columns = new String[] {
                DBConfiguration.KEY_NAME,
                DBConfiguration.KEY_CITY,
                DBConfiguration.KEY_REASON,
                DBConfiguration.KEY_BUDGET
              };
    // the XML defined views which the data will be bound to 
    int[] to = new int[]{
             R.id.TV_trip_name,
             R.id.TV_city_name,
             R.id.TV_trip_reason,
             R.id.TV_budget,         
    };

    //create the adapter using the cursor pointing to the desired data 
    //as well as the layout information

    dataAdapter = new SimpleCursorAdapter(this, R.layout.history_list_item, cursor, columns, to, 0);

    ListView listView = (ListView) findViewById(R.id.listView_tripHistory);
     // Assign adapter to ListView
    listView.setAdapter(dataAdapter);

    listView.setOnItemClickListener(new OnItemClickListener() {

        @Override
        public void onItemClick(AdapterView<?> listView, View view, int position, long id) {

            intentMethod(id);   

        }

        private void intentMethod(long ID) {

            //Bundle basket_tripID = new Bundle();
            //basket_tripID.putExtra("key_ID",TripID);

            TripID = ID;

            Intent Openactivity = new Intent(HistoryListActivity.this, HistoryViewerActivity.class);
            //Openactivity.putExtra("key_ID",id);
            startActivity(Openactivity);

        }
    });
}

protected void onPause() {
    super.onPause();
    finish();
}


}

这里的接收活动：

TextView TripName, TripReason, cityName, SD, AD, budget, HE, TE, FE, EE, SE, OE, RemainBudget;

ImageButton CheckedIn;

long idDB = HistoryListActivity.TripID;

String name ;

String city;
String reason;
String startingdate;
String arrivaldate;
String tbudget;

int hexp;
int texp;
int fexp;
int eexp;
int sexp;
int oexp;

int rbudget;

TrackerDAO dbHelper;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_history_viewer);

    TripName = (TextView) findViewById(R.id.textView_History_TripName);

    cityName = (TextView) findViewById(R.id.textView_History_CityName);
    TripReason = (TextView) findViewById(R.id.textView_History_TripReason);
    SD = (TextView) findViewById(R.id.textView_History_SD);
    AD = (TextView) findViewById(R.id.textView__History_AD);
    budget = (TextView) findViewById(R.id.textView_History_Budget);

    HE = (TextView) findViewById(R.id.textView_History_Hotel);
    TE = (TextView) findViewById(R.id.textView_History_Transport);
    FE = (TextView) findViewById(R.id.textView__History_Food);
    EE = (TextView) findViewById(R.id.textView_History_Entertainment);
    SE = (TextView) findViewById(R.id.textView_History_Shopping);
    OE = (TextView) findViewById(R.id.textView_History_Other);
    RemainBudget = (TextView) findViewById(R.id.textView_History_RemainingBudget);

    CheckedIn = (ImageButton) findViewById(R.id.imageButton_CheckedIN);

    displayshowHistory(idDB);

    TripName.setText(name);
    cityName.setText(city);
    TripReason.setText(reason);
    SD.setText(startingdate);
    AD.setText(arrivaldate);
    budget.setText(tbudget);
    HE.setText(String.valueOf(hexp));
    TE.setText(String.valueOf(texp));
    FE.setText(String.valueOf(fexp));
    EE.setText(String.valueOf(eexp));
    SE.setText(String.valueOf(sexp));
    OE.setText(String.valueOf(oexp));
    RemainBudget.setText(String.valueOf(rbudget));

    CheckedIn.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View v) {


        }
    });

}

private void displayshowHistory(long id) {

        dbHelper.open();

        Cursor cursor = dbHelper.getInfo(id);

        if (cursor.moveToFirst()) {
            //idDB = cursor.getLong(TrackerDAO.COL_ROWID);
            name = cursor.getString(TrackerDAO.COL_NAME);
            city = cursor.getString(TrackerDAO.COL_CITY);
            reason = cursor.getString(TrackerDAO.COL_REASON);
            startingdate = cursor.getString(TrackerDAO.COL_SOD);
            arrivaldate = cursor.getString(TrackerDAO.COL_AD);
            tbudget = cursor.getString(TrackerDAO.COL_BUDGET);

            hexp = cursor.getInt(TrackerDAO.COL_HE);
            texp = cursor.getInt(TrackerDAO.COL_TE);
            fexp = cursor.getInt(TrackerDAO.COL_FE);
            eexp = cursor.getInt(TrackerDAO.COL_EE);
            sexp = cursor.getInt(TrackerDAO.COL_SE);
            oexp = cursor.getInt(TrackerDAO.COL_OE);
            rbudget = cursor.getInt(TrackerDAO.COL_REMAINBUDGET);

            /*historyString = "Trip Name: " + tripname + "\n"
                    + "City: " + city + "\n"
                    + "Reason For travel: " + tripreason + "\n"
                    + "Starting Date: " + sd + "\n"
                    + "Date of Arrival: " + ad + "\n"
                    + "Estimated Budget: " + tbudget + "\n"
                    + "Hotel Rents: " + he + "\n"
                    + "Tansport Fares: " + te + "\n"
                    + "Food Costs: " + fe + "\n"
                    + "Entertainment Spendings: " + ee + "\n"
                    + "Shopping Expenditure: " + se + "\n"
                    + "Other Expenses: "  + oe + "\n"
                    + "Remain Money: " + rbudget; */
        }

        dbHelper.close(); 

    }
 }

现在这里是LOGCAT：

01-28 08:23:56.612: E/AndroidRuntime(1140): FATAL EXCEPTION: main
01-28 08:23:56.612: E/AndroidRuntime(1140): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.blackcat.triporganizer/com.blackcat.triporganizer.history.HistoryViewerActivity}: java.lang.NullPointerException
01-28 08:23:56.612: E/AndroidRuntime(1140):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2211)
01-28 08:23:56.612: E/AndroidRuntime(1140):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2261)
01-28 08:23:56.612: E/AndroidRuntime(1140):     at android.app.ActivityThread.access$600(ActivityThread.java:141)
01-28 08:23:56.612: E/AndroidRuntime(1140):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1256)
01-28 08:23:56.612: E/AndroidRuntime(1140):     at android.os.Handler.dispatchMessage(Handler.java:99)
01-28 08:23:56.612: E/AndroidRuntime(1140):     at android.os.Looper.loop(Looper.java:137)
01-28 08:23:56.612: E/AndroidRuntime(1140):     at android.app.ActivityThread.main(ActivityThread.java:5103)
01-28 08:23:56.612: E/AndroidRuntime(1140):     at java.lang.reflect.Method.invokeNative(Native Method)
01-28 08:23:56.612: E/AndroidRuntime(1140):     at java.lang.reflect.Method.invoke(Method.java:525)
01-28 08:23:56.612: E/AndroidRuntime(1140):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737)
01-28 08:23:56.612: E/AndroidRuntime(1140):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
01-28 08:23:56.612: E/AndroidRuntime(1140):     at dalvik.system.NativeStart.main(Native Method)
01-28 08:23:56.612: E/AndroidRuntime(1140): Caused by: java.lang.NullPointerException
01-28 08:23:56.612: E/AndroidRuntime(1140):     at com.blackcat.triporganizer.history.HistoryViewerActivity.displayshowHistory(HistoryViewerActivity.java:92)
01-28 08:23:56.612: E/AndroidRuntime(1140):     at com.blackcat.triporganizer.history.HistoryViewerActivity.onCreate(HistoryViewerActivity.java:63)
01-28 08:23:56.612: E/AndroidRuntime(1140):     at android.app.Activity.performCreate(Activity.java:5133)
01-28 08:23:56.612: E/AndroidRuntime(1140):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
01-28 08:23:56.612: E/AndroidRuntime(1140):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2175)
01-28 08:23:56.612: E/AndroidRuntime(1140):     ... 11 more

Answer 1

我认为你在null pointer exception方法中得到displayshowHistory()。问题可能是该方法中未初始化的对象。所以请检查是否有任何未初始化的对象。

Answer 2

在我的情况下，我刚刚将第二个活动添加到Manifest文件中，并且每件事都变得正常：

添加：<activity android:name=".MainActivity2"></activity>

注意：通过第二项活动更改MainActivity2。

你的最终文件将是这样的：

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.sadmi.darksnow.intentbundle">

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <activity android:name=".MainActivity2"></activity>
    </application>

</manifest>

致命异常：主要，无法启动活动ComponentInfo

2 个答案: