填充ListAdapter

Question

我处于某种程度，我需要一些帮助。我现在坚持这个问题几天了。 （我是Android编程的新手）

所以我在我的第一个应用程序中，想要创建一个ListView，其中填充了SQLite数据库中的条目。

不幸的是，当我尝试设置我的适配器时，我得到了NullPointerException。

我希望你们有一个想法，如何解决这个或暗示我可以照顾解决方案。对于这段代码，我经历了几个教程，所以我可能会错过一些重要的部分，或者做了一个相当＆＃34;愚蠢的＆＃34;因为我是一个完整的新手。

继承我的守则：

方法，填充ListView：

//Populates the List View
public void readDB(View view){

    Log.d("ReadDB","Start");

    //Read DB
    Cursor myCursor = dbTimer.rawQuery("Select * from Times", null);
    myCursor.moveToFirst();

    //Outputs DB-Entries in Console (for checking if there are entries)
    printDB(myCursor);

    //Find ListView to populate
    lvItems = (ListView) findViewById(R.id.listView_timer);

    //Setup Cursor Adapter with the ResultSet
    TimerCursorAdapter myAdapter = new TimerCursorAdapter(this, myCursor);

    //Attach Cursor adapter to the ListView
    lvItems.setAdapter(myAdapter);
    Log.d("ReadDB","Finish");

}

适配器类

public class TimerCursorAdapter extends CursorAdapter {

public TimerCursorAdapter(Context context, Cursor cursor){
    super(context, cursor, 0);
}

@Override
public View newView(Context context, Cursor cursor, ViewGroup parent){
    return LayoutInflater.from(context).inflate(R.layout.item_list_view, parent, false);
}

@Override
public void bindView(View view, Context context, Cursor cursor){

    // Find TextFields for pupolation
    TextView tvTitle = (TextView) view.findViewById(R.id.textView_title);
    TextView tvCup = (TextView) view.findViewById(R.id.textView_cup);
    TextView tvGram = (TextView) view.findViewById(R.id.textView_gram);
    TextView tvMilliliter = (TextView) view.findViewById(R.id.textView_milliliter);
    TextView tvBlooming = (TextView) view.findViewById(R.id.textView_blooming);
    TextView tvSteeping = (TextView) view.findViewById(R.id.textView_steeping);
    TextView tvPressing = (TextView) view.findViewById(R.id.textView_pressing);

    // Extract properties from Cursor
    String strTitle = cursor.getString(cursor.getColumnIndexOrThrow("Title"));
    String intCup = cursor.getString(cursor.getColumnIndexOrThrow("Cup"));
    String intGram = cursor.getString(cursor.getColumnIndexOrThrow("Gram"));
    String intMilliliter = cursor.getString(cursor.getColumnIndexOrThrow("Milliliter"));
    String intBlooming = cursor.getString(cursor.getColumnIndexOrThrow("Blooming"));
    String intSteeping = cursor.getString(cursor.getColumnIndexOrThrow("Steeping"));
    String intPressing = cursor.getString(cursor.getColumnIndexOrThrow("Pressing"));

    //Sets TextVies in the Layout
    tvTitle.setText(strTitle);
    tvCup.setText(intCup);
    tvGram.setText(intGram);
    tvMilliliter.setText(intMilliliter);
    tvBlooming.setText(intBlooming);
    tvSteeping.setText(intSteeping);
    tvPressing.setText(intPressing);
}

错误代码

10-06 12:03:16.064 862-862/clausing.sebastian.de.eztimer E/AndroidRuntime: FATAL EXCEPTION: main
Process: clausing.sebastian.de.eztimer, PID: 862
Theme: themes:{}
java.lang.IllegalStateException: Could not execute method for android:onClick
at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:289)
at android.view.View.performClick(View.java:5204)
at android.view.View$PerformClick.run(View.java:21158)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5461)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
Caused by: java.lang.reflect.InvocationTargetException
at java.lang.reflect.Method.invoke(Native Method)
at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:284)
at android.view.View.performClick(View.java:5204) 
at android.view.View$PerformClick.run(View.java:21158) 
at android.os.Handler.handleCallback(Handler.java:739) 
at android.os.Handler.dispatchMessage(Handler.java:95) 
at android.os.Looper.loop(Looper.java:148) 
at android.app.ActivityThread.main(ActivityThread.java:5461) 
at java.lang.reflect.Method.invoke(Native Method) 
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726) 
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616) 
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.ListView.setAdapter(android.widget.ListAdapter)' on a null object reference
at clausing.sebastian.de.eztimer.MainActivity.readDB(MainActivity.java:114)
at java.lang.reflect.Method.invoke(Native Method) 
at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:284) 
at android.view.View.performClick(View.java:5204) 
at android.view.View$PerformClick.run(View.java:21158) 
at android.os.Handler.handleCallback(Handler.java:739) 
at android.os.Handler.dispatchMessage(Handler.java:95) 
at android.os.Looper.loop(Looper.java:148) 
at android.app.ActivityThread.main(ActivityThread.java:5461) 
at java.lang.reflect.Method.invoke(Native Method) 
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726) 
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)