Question

我有四节课： MainActivity.java - MyAdapter.java - MyDataBase.java - MyListActivity.java

现在，MyListActiviy中的Uri是什么？我怎么能填写它？当我点击MainActivity中的“showlist_btn”按钮时，会显示一个没有内容的列表！为什么？

MainActivity：

package com.example.ex22;

import android.os.Bundle;
import android.app.Activity;
import android.content.Intent;
import android.view.Menu;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;

public class MainActivity extends Activity {
EditText edittext ;
Button add_btn ;
Button showlist_btn ;
MyDataBase mydatabase ;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    mydatabase = new MyDataBase(MainActivity.this);
    edittext = (EditText)findViewById(R.id.edittext);
    showlist_btn = (Button)findViewById(R.id.showlist_btn);
    add_btn = (Button)findViewById(R.id.add_btn);
    add_btn.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View v) {
            // TODO Auto-generated method stub
            String str = edittext.getText().toString();
            mydatabase.addName(str);
            edittext.setText("");
        }
    });

    showlist_btn.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View v) {
            // TODO Auto-generated method stub
            Intent intent = new Intent(MainActivity.this,   MyListActivity.class);
            startActivity(intent);
        }
    });
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.activity_main, menu);
    return true;
}

}

MyAdapter：

package com.example.ex22;

import java.util.List;

import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.TextView;

public class MyAdapter extends BaseAdapter  {
List<String> mylist ;
LayoutInflater inflater ;
public MyAdapter(Context context){
    inflater = LayoutInflater.from(context);
}
@Override
public int getCount() {
    // TODO Auto-generated method stub
    return mylist.size();
}

void getList(List<String> list){
    mylist = list ;
}

@Override
public Object getItem(int position) {
    // TODO Auto-generated method stub
    return position;
}

@Override
public long getItemId(int position) {
    // TODO Auto-generated method stub
    return position;
}

@Override
public View getView(int position, View convertView, ViewGroup parent) {
    // TODO Auto-generated method stub
    ViewHolder viewholder ;
    if(convertView == null){
        convertView = inflater.inflate(R.layout.row_for_list, null);
        viewholder = new ViewHolder();
        viewholder.text =     (TextView)convertView.findViewById(R.id.textview_forrow);
        convertView.setTag(viewholder);
    }else {
        viewholder = (ViewHolder)convertView.getTag();
    }
    viewholder.text.setText(mylist.get(position));
    return convertView;
}

static class ViewHolder{

    TextView text ;
}

}

MYDATABASE：

package com.example.ex22;

import java.util.ArrayList;
import java.util.List;

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

public class MyDataBase extends SQLiteOpenHelper {

private final static String DB_NAME = "mydb" ;
private final static String TABLE_NAME = "mytable" ;
//private static final String NAME = "name" ;
private final static String NAME_COLOUM = "_name" ;

private static final String CREATE_TABLE = "CREATE TABLE "+ TABLE_NAME + "("
        + NAME_COLOUM + " TEXT" + ")";

public MyDataBase(Context context){
    super(context,DB_NAME,null,1);
}
@Override
public void onCreate(SQLiteDatabase db) {
    // TODO Auto-generated method stub
    db.execSQL(CREATE_TABLE);

}

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    // TODO Auto-generated method stub
    db.execSQL("DROP TABLE IF EXISTS " + TABLE_NAME);
}

public void addName(String str){
    SQLiteDatabase db = this.getWritableDatabase();
    ContentValues values = new ContentValues();
    values.put(NAME_COLOUM, str);
    db.insert(TABLE_NAME, null, values);
    db.close();
}

public List<String> getAllNames(){
    List<String> list = new ArrayList<String>() ;
    SQLiteDatabase db = this.getWritableDatabase();

    Cursor c = db.rawQuery("SELECT * FROM "+ TABLE_NAME, null);
    if(c.moveToFirst()){
        do{String str = c.getString(0);
        list.add(str);
        }while(c.moveToNext());

    }

    return list ;


}

public String getCulomName(){

    return this.NAME_COLOUM;
}

}

MyListActivity：

package com.example.ex22;

import android.app.ListActivity;
import android.app.LoaderManager;
import android.app.LoaderManager.LoaderCallbacks;
import android.content.CursorLoader;
import android.content.Loader;
import android.database.Cursor;
import android.net.Uri;
import android.os.Bundle;
import android.widget.SimpleCursorAdapter;

public class MyListActivity extends ListActivity
implements LoaderCallbacks<Cursor>{
SimpleCursorAdapter simplecursorradapter ;
MyDataBase mydb ;
CursorLoader cursorloader ;
@Override
protected void onCreate(Bundle savedInstanceState) {
    // TODO Auto-generated method stub
    super.onCreate(savedInstanceState);
    //setContentView(R.layout.show_list);
    mydb = new MyDataBase(this);
    String[] from = new String[] { mydb.getCulomName() };
    int[] to = new int[]{
            R.id.forlist
    };
    simplecursorradapter = new SimpleCursorAdapter(this,      android.R.layout.simple_expandable_list_item_2, null,
            from , to ,0);
    setListAdapter(simplecursorradapter);
    LoaderManager loadermanager = getLoaderManager();
    loadermanager.initLoader(0, null, this);
}

@Override
public Loader<Cursor> onCreateLoader(int id, Bundle args) {
    // TODO Auto-generated method stub



    String[] projection = {mydb.getCulomName()};
    final String SCHEME = "content";

    // The provider's authority
    final String AUTHORITY = "com.example.ex22";
    final Uri src = Uri.parse(SCHEME + "://" + AUTHORITY);
    Uri uri = Uri.withAppendedPath(src, "mytable");
     cursorloader = new CursorLoader(this, uri, projection, null, null, null);
    return cursorloader;
}

@Override
public void onLoadFinished(Loader<Cursor> arg0, Cursor arg1) {
    // TODO Auto-generated method stub
    simplecursorradapter.swapCursor(arg1);
}

@Override
public void onLoaderReset(Loader<Cursor> arg0) {
    // TODO Auto-generated method stub
    simplecursorradapter.swapCursor(null);
}



}

activity_main：

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
tools:context=".MainActivity" >

<EditText 
    android:id="@+id/edittext"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:hint="Write Your Name..."
    />
<Button 
    android:id="@+id/add_btn"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:text="Add Name"
    />
<Button 
    android:id="@+id/showlist_btn"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:text="Show Name List"
    />

</LinearLayout>

forlist：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >
<TextView 
    android:id="@+id/forlist"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    />

</LinearLayout>

row_for_list：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent">

<TextView 
    android:id="@+id/textview_forrow"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:textSize="40sp"
    />

</LinearLayout>

show_list：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >

<ListView
    android:id="@android:id/list"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
     />

Uri参数和LoaderCallbacks

0 个答案: