Question

我在面对应用程序吃午饭时面临崩溃，我试图从微调器中选择值并将其设置在文本视图中。没有微调器，它工作得很好。现在它根本不起作用。提前谢谢你

这是主要活动

public class MainActivity extends AppCompatActivity implements    AdapterView.OnItemSelectedListener {
DB db;
Button addmed,addpl;
TextView PPLNAMERES;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    db = new DB(this);
    ArrayList<String> my_array= new ArrayList<String>();
    my_array = db.getTableValues();
    Spinner spinner = (Spinner)findViewById(R.id.spin1);
    ArrayAdapter<String> my_adapter = new ArrayAdapter(this,R.layout.support_simple_spinner_dropdown_item,my_array);
    spinner.setAdapter(my_adapter);
    spinner.setOnItemSelectedListener(this);
    PPLNAMERES = (TextView)findViewById(R.id.PPLAGETXTVIEW);
}


public void addmedView(View view){
    Intent ADDMEDVIEW = new Intent(this,ADDMEDCINEVIEW.class);
    startActivity(ADDMEDVIEW);

}
public void addpplview(View view){
    Intent ADDPPLVIEWS = new Intent(this,ADDPPLVIEW.class);
    startActivity(ADDPPLVIEWS);
}



public void listView(int index){
int getPPLNAME = index;
Cursor res= db.getMainData();
    if(res.moveToFirst()){
        PPLNAMERES.setText(res.getString(getPPLNAME));
    } else{
        Toast.makeText(MainActivity.this,"No Data",Toast.LENGTH_LONG).show();
        return;
    }
}


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

    listView(position);

}

@Override
public void onNothingSelected(AdapterView<?> parent) {

}
}

sqliteopenhelper类

public class DB extends SQLiteOpenHelper {

public final static String DBNAME = "MEDCINEDB.db";
public final static String Table_name = "MEDCINETable";
public final static String Table_name2 = "PPLTABLE";
public final static String col1 = "MEDCINEID";
public final static String col2 = "MEDCINENAME";
public final static String col3 = "MEDCINEPURPOSE";
public final static String col4 = "NOTAPLET";
public final static String col1T2 = "ID";
public final static String col2T2 = "NAMEPPL";
public final static String col3T2 = "AGEPPL";
public final static int DBVersion = 2;


public DB(Context context) {
    super(context, DBNAME, null, DBVersion);
}

@Override
public void onCreate(SQLiteDatabase db) {
    db.execSQL("CREATE TABLE " + Table_name + "(MEDCINEID INTEGER PRIMARY KEY AUTOINCREMENT,MEDCINENAME TEXT,MEDCINEPURPOSE TEXT,NOTAPLET INTEGER)");
    db.execSQL("CREATE TABLE " + Table_name2 + "(ID INTEGER PRIMARY KEY AUTOINCREMENT,NAMEPPL TEXT,AGEPPL INTEGER)");
}

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    db.execSQL("DROP IF EXISTS" + Table_name);
    db.execSQL("DROP IF EXISTS" + Table_name2);
    onCreate(db);

}

public boolean inserData(String name, String purpose, String notaplet) {
    SQLiteDatabase db = this.getWritableDatabase();
    ContentValues contentValues = new ContentValues();
    contentValues.put(col2, name);
    contentValues.put(col3, purpose);
    contentValues.put(col4, notaplet);

    long Result = db.insert(Table_name, null, contentValues);
    if (Result == -1) {
        return false;
    } else {
        return true;
    }
}

public boolean insertTb2Data(String Name, String Age) {
    SQLiteDatabase db = getWritableDatabase();
    ContentValues PPLcontentValues = new ContentValues();
    PPLcontentValues.put(col2T2, Name);
    PPLcontentValues.put(col3T2, Age);
    Long Result = db.insert(Table_name2, null, PPLcontentValues);
    if (Result == -1) {
        return false;
    } else
        return true;
}

public Cursor getMainData() {
    SQLiteDatabase db = this.getWritableDatabase();
    Cursor result = db.rawQuery("select NAMEPPL from " + Table_name2, null);
    return result;

}

public ArrayList<String> getTableValues() {

    ArrayList<String> my_array = new ArrayList<String>();
    try {
        SQLiteDatabase db = this.getWritableDatabase();
        Cursor resultPPNAME = db.rawQuery("select NAMEPPL from " + Table_name2, null);
        resultPPNAME.moveToFirst();
        while (resultPPNAME.isAfterLast() == false) {
            String PPLNAMESPIN = resultPPNAME.getString(0);
            resultPPNAME.moveToNext();
            my_array.add(PPLNAMESPIN);
        }


    } catch (Exception e) {

    }

    return my_array;

}
}

logcat中的

告诉我这条消息

java.lang.NullPointerException：尝试在空对象引用上调用虚方法'void android.widget.TextView.setText（java.lang.CharSequence）'

Answer 1

在PPLNAMERES中，TextView希望显示Spinner中的选定文本，然后将listView方法更改为：

public void listView(int index){
  PPLNAMERES.setText(my_array.get(index));
}

同样在create方法上声明my_array与声明的PPLNAMERES和其他变量相同的方式。

从sqlite获取数据并在spinner的文本视图中设置它

1 个答案: