为什么当我点击我的按钮时我的应用程序崩溃了，我该如何修复它？

我需要在单击按钮时将行插入到我的SQLite数据库中。它包含两个值，这应该很容易。一个是 date，使用 simpledateformatter 格式化。另一个只是 ArrayList 中的一个位置。我的代码中没有红线，但当我按下按钮以插入行时，我的应用程序崩溃了。下面是来自 3 个 Java 文件的代码，这些文件相互交互。我有预感问题出在我的 Model.java 上，但它可能不止于此。如果需要更多代码，请询问。

MainActivity.java

public class MainActivity extends Activity {
final String TAG = "*** DEBUG ***";

public static final String SMOKIN_DATA_FILE = "smokin.dat";
public static final int EDIT_ACTIVITY = 1;

public static Model model = null;
public static MySmokinDatabase mySmokinDatabase;
public static Cursor cursor;
public static SimpleCursorAdapter adapter;

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    setContentView(R.layout.activity_main);

    restoreModel();

    if (mySmokinDatabase == null)
        mySmokinDatabase = new MySmokinDatabase(this);

    refreshView();
}

@Override
protected void onResume() {
    super.onResume();

    if (model == null)
        restoreModel();

    refreshView();
}

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

    saveModel();
}

private void refreshView() {
    Spinner spinner = (Spinner) findViewById(R.id.location_spinner);

    ArrayAdapter<String> adapter = new ArrayAdapter<String>(this,
             android.R.layout.simple_spinner_item, model.getLocationsArray());

    adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);

    spinner.setAdapter(adapter);

    SimpleDateFormat sdf = new SimpleDateFormat("E, MMM dd");

    TextView dateText = (TextView) findViewById(R.id.date);
    TextView countText = (TextView) findViewById(R.id.count);
    TextView daysText = (TextView) findViewById(R.id.days);
    TextView totalText = (TextView) findViewById(R.id.total);
    TextView aveText = (TextView) findViewById(R.id.ave);

    GregorianCalendar now = new GregorianCalendar();
    dateText.setText(sdf.format(now.getTime()));
    //get today's count from data in the SQLite table - count entries with today's date
    countText.setText("" + "");
    //mySmokinDatabase.getTodaysCount());

    // Table data
    daysText.setText("" + String.format("%10d", model.getDays()));
    totalText.setText("" + "get total count from data in SQLite table - count total rows");

    if (model.getDays() > 0)
        aveText.setText("calc average from SQLite and model info");

}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    getMenuInflater().inflate(R.menu.activity_main, menu);
    return true;
}

@Override
public void onActivityResult(int requestCode, int resultCode, Intent data)  { 
    super.onActivityResult(requestCode, resultCode, data); 
    if (resultCode == RESULT_OK && requestCode == EDIT_ACTIVITY) { 
        saveModel();
    }
}

public void smokedHandler(View view) {
    Spinner spinner = (Spinner) findViewById(R.id.location_spinner);

    String s = spinner.getSelectedItem().toString();
    String d = model.getDates();

    mySmokinDatabase.insertSmokinValues(new Model(s,d));

    cursor = mySmokinDatabase.getAllSmokinCursor();
    adapter.changeCursor(cursor);   

    refreshView();
}

public void restoreModel() {
    // Restore from disk, or start with an empty model
    try {
        ObjectInputStream ois = new ObjectInputStream(
                openFileInput(SMOKIN_DATA_FILE));

        model = (Model) ois.readObject();
        ois.close();
    }
    catch (Exception e){
        Log.v("*** DEBUG ***", "Error writing to file: " + e);
        model = new Model();
    }
}

public void saveModel() {
    Log.v("*** AJ ***", "In onPause");

    try {
        ObjectOutputStream oos = new ObjectOutputStream(
                openFileOutput(SMOKIN_DATA_FILE, Context.MODE_PRIVATE));

        oos.writeObject(model);
        oos.close();
    }
    catch (Exception e){
        Log.v("*** MatchIt ***", "Error writing to file: " + e);
    }
}

数据库文件

public long insertSmokinValues(Model model) {
    ContentValues newSmokinValues = new ContentValues();
    newSmokinValues.put(KEY_DATE, model.getDates());
    newSmokinValues.put(KEY_LOCATION, model.getLocations());        
    SQLiteDatabase db = smokinDBOpenHelper.getWritableDatabase();

    return db.insert(SmokinDBOpenHelper.INCIDENTS_TABLE, null, newSmokinValues);
}

public Cursor getAllSmokinCursor() {
    SQLiteDatabase db = smokinDBOpenHelper.getWritableDatabase();

    return db.query(SmokinDBOpenHelper.INCIDENTS_TABLE, new String[] 
            {KEY_ID, KEY_LOCATION, KEY_DATE}, null, null, null, null, null);        
}

模型文件

private ArrayList<String> locations = new ArrayList<String>();
public String [] defaultLocations = {"Home", "Work", "Commuting", "School", "Bar", 
"Restaurant", "Social Gathering", "Other"};

public Model(GregorianCalendar date){
    startDate = date;

    for (String s : this.defaultLocations)
        locations.add(s);
}

public Model(String s, String d) {
    place = s;
    dates = d;      
}

public String getDates() {
    GregorianCalendar gc = new GregorianCalendar();
    SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm");
    dates = sdf.format(gc.getTime());       

    return dates;
}   

public String getLocations() {
    for (String s : this.locations)
        place = s;
    return place;
}       

根据请求日志猫:

 03-18 15:52:42.397: W/dalvikvm(676): threadid=1: thread exiting with uncaught  
 exception
 (group=0x40a13300)
 03-18 15:52:42.457: E/AndroidRuntime(676): FATAL EXCEPTION: main
03-18 15:52:42.457: E/AndroidRuntime(676): java.lang.IllegalStateException: Could not    
execute method of the activity
03-18 15:52:42.457: E/AndroidRuntime(676):  at    
android.view.View$1.onClick(View.java:3591)
03-18 15:52:42.457: E/AndroidRuntime(676):  at   
android.view.View.performClick(View.java:4084)
03-18 15:52:42.457: E/AndroidRuntime(676):  at   
android.view.View$PerformClick.run(View.java:16966)
03-18 15:52:42.457: E/AndroidRuntime(676):  at   
android.os.Handler.handleCallback(Handler.java:615)
03-18 15:52:42.457: E/AndroidRuntime(676):  at   
android.os.Handler.dispatchMessage(Handler.java:92)
03-18 15:52:42.457: E/AndroidRuntime(676):  at android.os.Looper.loop(Looper.java:137)
03-18 15:52:42.457: E/AndroidRuntime(676):  at   
android.app.ActivityThread.main(ActivityThread.java:4745)
03-18 15:52:42.457: E/AndroidRuntime(676):  at    
java.lang.reflect.Method.invokeNative(Native Method)
03-18 15:52:42.457: E/AndroidRuntime(676):  at 
java.lang.reflect.Method.invoke(Method.java:511)
03-18 15:52:42.457: E/AndroidRuntime(676):  at 
com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
03-18 15:52:42.457: E/AndroidRuntime(676):  at    
com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
03-18 15:52:42.457: E/AndroidRuntime(676):  at dalvik.system.NativeStart.main(Native   
Method)
03-18 15:52:42.457: E/AndroidRuntime(676): Caused by: 
java.lang.reflect.InvocationTargetException
03-18 15:52:42.457: E/AndroidRuntime(676):  at   
java.lang.reflect.Method.invokeNative(Native Method)
03-18 15:52:42.457: E/AndroidRuntime(676):  at   
java.lang.reflect.Method.invoke(Method.java:511)
03-18 15:52:42.457: E/AndroidRuntime(676):  at   
android.view.View$1.onClick(View.java:3586)
03-18 15:52:42.457: E/AndroidRuntime(676):  ... 11 more
03-18 15:52:42.457: E/AndroidRuntime(676): Caused by: java.lang.NullPointerException
03-18 15:52:42.457: E/AndroidRuntime(676):  at     
com.example.smokin4ThomasSullivan.MainActivity.smokedHandler(MainActivity.java:119)
03-18 15:52:42.457: E/AndroidRuntime(676):  ... 14 more

line 119: adapter.changeCursor(cursor); The method involved is posted in my DB file

一如既往地感谢任何帮助!

最佳答案

日志说明了一切:您正在尝试使用 adapter，它在此行中为 null:

adapter.changeCursor(cursor); 

编辑:

如我所想，您在这里声明了您的适配器字段:

public static SimpleCursorAdapter adapter;

但是您没有初始化它，正如您在 Java 中应该知道的那样，如果您在没有初始化的情况下声明一个字段，它将被设置为 null。这就是您收到错误的原因。

我没有亲自使用过 SimpleCursorAdapter 类，但您可能想看看它的构造函数，它在 android 文档中有描述: http://developer.android.com/reference/android/widget/SimpleCursorAdapter.html

所以基本上在 onCreate() 方法中，你应该做这样的事情:

adapter = new SimpleCursorAdapter( this, 
                                   R.layout.some_layout,
                                   cursor,
                                   columns,
                                   to,
                                   0 );

在我之前发布链接的文档中描述了使用的构造函数的参数。

您可能还想检查使用 SimpleCursorAdapter 的这段代码: http://www.mysamplecode.com/2012/07/android-listview-cursoradapter-sqlite.html

关于android - 单击按钮插入，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/15486065/