Question

嗨，我是一个全新的编程，我不知道为什么我的代码无法在片段中工作，我关注了newboston视频并进行了一些更改但它仍然无法正常工作，当我尝试保存时它会崩溃里面的价值。我添加了一个rootview，但除此之外，我认为我什么都没做，有人介意帮助一个可怜的灵魂出去吗？

package com.example.onTV;

import android.app.Fragment;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.EditText;
import android.widget.TextView;


public class HistoryFragment extends Fragment {
    EditText name;
    TextView sqlDisplay;
    MyDBHandler dbHandler;

    public HistoryFragment() {


    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {

        View rootView = inflater.inflate(R.layout.fragment_history, container, false);
        name = (EditText) rootView.findViewById(R.id.name);
        sqlDisplay = (TextView) rootView.findViewById(R.id.sqlDisplay);
        dbHandler = new MyDBHandler(this.getActivity(), null, null, 1);
        printDatabase();
        return rootView;


    }

    //Add a product to the database

    public void saveOnClicked(View view) {
        favourites favourites = new favourites(name.getText().toString());
        dbHandler.addFavourites(favourites);
        printDatabase();
    }

    //Delete items
    public void deleteOnClicked(View view) {
        String inputText = name.getText().toString();
        dbHandler.deleteFavourites(inputText);
        printDatabase();
    }

    //Print the database
    public void printDatabase() {
        String dbString = dbHandler.databaseToString();
        sqlDisplay.setText(dbString);
        name.setText("");
    }
}

dbhandler类

package com.example.onTV;

import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;

public class MyDBHandler extends SQLiteOpenHelper{

public static final int DATABASE_VERSION = 2;
public static final String DATABASE_NAME ="favourites.db";
public static final String TABLE_FAVOURITES = "favourites";
public static final String COLUMN_ID = "_id";
public static final String COLUMN_VIDEONAME = "videoname";
// public static final String COLUMN_LINK = "link";

public MyDBHandler(Context context, String name, SQLiteDatabase.CursorFactory factory, int version) {
    super(context, DATABASE_NAME, factory, DATABASE_VERSION);
}

@Override
public void onCreate(SQLiteDatabase db) {
    String query = "CREATE TABLE " + TABLE_FAVOURITES + "(" +
            COLUMN_ID + " INTEGER PRIMARY KEY AUTOINCREMENT, " +
            COLUMN_VIDEONAME + " TEXT " +/* COLUMN_LINK + " TEXT " +*/
            ");";
    db.execSQL(query);

}

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    db.execSQL("DROP TABLE IF EXISTS " + TABLE_FAVOURITES);
    onCreate(db);
}
public void addFavourites(favourites favourites){
    ContentValues values = new ContentValues();
    values.put(COLUMN_VIDEONAME, favourites.get_videoname());
  //  values.put(COLUMN_LINK, favourites.get_link());
    SQLiteDatabase db = getWritableDatabase();
    db.insert(TABLE_FAVOURITES, null, values);
    db.close();
}
public void deleteFavourites(String videoName){
    SQLiteDatabase db = getWritableDatabase();

    db.execSQL("DELETE FROM " + TABLE_FAVOURITES + " WHERE " + COLUMN_VIDEONAME + "=\"" + videoName + "\" ;"
    //        + COLUMN_LINK + "=\"" + link + "\" ;"
    );
}
public String databaseToString(){
    String dbString = "";
    SQLiteDatabase db = getWritableDatabase();
    String query = "SELECT * FROM " + TABLE_FAVOURITES + " WHERE 1";

    //Cursor points to a location in your results
    Cursor c = db.rawQuery(query, null);
    //Move to the first row in your results
    c.moveToFirst();

    //Position after the last row means the end of the results
    while (!c.isAfterLast()) {
        if (c.getString(c.getColumnIndex("videoname")) != null) {
            dbString += c.getString(c.getColumnIndex("videoname"));
            dbString += "\n";

        }
        c.moveToNext();
    }
    db.close();
    return dbString;
}
}

日志出来

07-29 18:08:44.554    8051-8051/com.example.navigationdrawerexample D/ViewRootImpl﹕ ViewPostImeInputStage ACTION_DOWN
07-29 18:08:44.624    8051-8051/com.example.navigationdrawerexample D/AndroidRuntime﹕ Shutting down VM
07-29 18:08:44.624    8051-8051/com.example.navigationdrawerexample E/AndroidRuntime﹕ FATAL EXCEPTION: main
    Process: com.example.navigationdrawerexample, PID: 8051
    java.lang.IllegalStateException: Could not find a method saveOnClicked(View) in the activity class com.example.onTV.MainActivity for onClick handler on view class android.widget.Button with id 'saveButton'
            at android.view.View$1.onClick(View.java:4234)
            at android.view.View.performClick(View.java:5191)
            at android.view.View$PerformClick.run(View.java:20916)
            at android.os.Handler.handleCallback(Handler.java:739)
            at android.os.Handler.dispatchMessage(Handler.java:95)
            at android.os.Looper.loop(Looper.java:145)
            at android.app.ActivityThread.main(ActivityThread.java:5944)
            at java.lang.reflect.Method.invoke(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:372)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1399)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1194)
     Caused by: java.lang.NoSuchMethodException: saveOnClicked [class android.view.View]
            at java.lang.Class.getMethod(Class.java:665)
            at android.view.View$1.onClick(View.java:4227)
            at android.view.View.performClick(View.java:5191)
            at android.view.View$PerformClick.run(View.java:20916)
            at android.os.Handler.handleCallback(Handler.java:739)
            at android.os.Handler.dispatchMessage(Handler.java:95)
            at android.os.Looper.loop(Looper.java:145)
            at android.app.ActivityThread.main(ActivityThread.java:5944)
            at java.lang.reflect.Method.invoke(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:372)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1399)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1194)
07-29 18:08:49.164    8051-8051/com.example.navigationdrawerexample I/Process﹕ Sending signal. PID: 8051 SIG: 9

Answer 1

在布局xml中，您定义了android:onClick个属性，其值为saveOnClicked，deleteOnClicked。 Android将在您的活动类中查找具有相同名称的方法。可悲的是，它不适用于碎片。

使用片段时，最好以编程方式设置OnClickListener。删除布局中的android:onClick属性，并在片段中实现类似的内容：

@Override
public void onViewCreated(View rootView, Bundle savedInstanceState) {
    rootView.findViewById(R.id.save_button).setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            saveOnClicked(v);
        }
    });
    rootView.findViewById(R.id.delete_button).setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            deleteOnClicked(v);
        }
    });
}

为什么我的SQLite仍无法处理我的片段

1 个答案: