Activity的使用(四):两个activity的交互

LunchList中用到数据库，首先创建一个数据库类，要继承SQLiteOpenHelper,要重载onCreate和onUpgrade的方法：

package com.example.activity_and_service;import android.content.Context;
import android.content.ContentValues;
import android.database.Cursor;
import android.database.SQLException;
import android.database.sqlite.SQLiteOpenHelper;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteQueryBuilder;public class RestaurantHelper extends SQLiteOpenHelper {private static final String DATABASE_NAME = "lunchlist.db";private static final int SCHEMA_VERSION = 1;public RestaurantHelper(Context context){super(context, DATABASE_NAME, null, SCHEMA_VERSION);}public void onCreate(SQLiteDatabase db){db.execSQL("CREATE TABLE restaurants (_id INTEGER PRIMARY KEY AUTOINCREMENT, name TEXT, address TEXT, type TEXT, notes TEXT);");}public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion){}public Cursor getAll(){return getReadableDatabase().rawQuery("SELECT _id, name, address, type, notes FROM restaurants ORDER BY name", null);}public Cursor getById(String id){String[] args = {id};return getReadableDatabase().rawQuery("SELECT _id, name, address, type, notes FROM  restaurants WHERE _ID =?", args);}public void insert(String name, String address, String type, String notes){ContentValues cv = new ContentValues();cv.put("name", name);cv.put("address", address);cv.put("type", type);cv.put("notes", notes);getWritableDatabase().insert("restaurants", "name", cv);}public void update(String id, String name, String address, String type, String notes){ContentValues cv = new ContentValues();String[] args = {id};cv.put("name", name);cv.put("address", address);cv.put("type", type);cv.put("notes", notes);getWritableDatabase().update("restaurants", cv, "_ID=?", args);}public String getName(Cursor c){return c.getString(1);}public String getAddress(Cursor c){return c.getString(2);}public String getType(Cursor c){return c.getString(3);}public String getNotes(Cursor c){return c.getString(4);}
}

在 LunchList中用到CursorAdapter,自定义个继承CursorAdapter的内部类：

package com.example.activity_and_service;import android.app.ListActivity;
import android.content.Context;
import android.content.Intent;
import android.database.Cursor;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuInflater;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.view.LayoutInflater;
import android.widget.AdapterView;
import android.widget.CursorAdapter;
import android.widget.ImageView;
import android.widget.ListView;
import android.widget.TextView;
import android.util.Log;public class LunchList extends ListActivity {public final static String ID_EXTRA = "apt.tutorial._ID";Cursor model = null;RestaurantAdapter adapter = null;RestaurantHelper helper = null;public void onCreate(Bundle savedInstanceState){super.onCreate(savedInstanceState);setContentView(R.layout.main);helper = new RestaurantHelper(this);//Log.d("onCreate", "" + helper);model = helper.getAll();startManagingCursor(model);adapter = new RestaurantAdapter(model);setListAdapter(adapter);}public void onDestroy(){super.onDestroy();Log.d("test", "" + helper);helper.close();}public void onListItemClick(ListView list, View view, int position, long id){Intent i = new Intent(LunchList.this, MainActivity.class);i.putExtra(ID_EXTRA, String.valueOf(id));startActivity(i);}public boolean onCreateOptionsMenu(Menu menu){new MenuInflater(this).inflate(R.menu.option, menu);return super.onCreateOptionsMenu(menu);}public boolean onOptionsItemSelected(MenuItem item){if (item.getItemId() == R.id.add) {startActivity(new Intent(LunchList.this, MainActivity.class));return true;}return super.onOptionsItemSelected(item);}class RestaurantAdapter extends CursorAdapter{RestaurantAdapter(Cursor c){super(LunchList.this, c);}public void bindView(View row, Context context, Cursor c){RestaurantHolder holder = (RestaurantHolder)row.getTag();holder.populateFrom(c, helper);}public View newView(Context context, Cursor c, ViewGroup parent){LayoutInflater inflater = getLayoutInflater();View row = inflater.inflate(R.layout.row, parent, false);RestaurantHolder holder = new RestaurantHolder(row);row.setTag(holder);return row;}}static class RestaurantHolder{private TextView name = null;private TextView address = null;private ImageView icon = null;RestaurantHolder(View row){name = (TextView)row.findViewById(R.id.title);address = (TextView)row.findViewById(R.id.address);icon = (ImageView)row.findViewById(R.id.icon);}void populateFrom(Cursor c, RestaurantHelper helper){//Log.d("populateFrom", "cursor:" + c);try {name.setText(helper.getName(c));address.setText(helper.getAddress(c));if ("sit_down".equals(helper.getType(c))) {icon.setImageResource(R.drawable.bg_video);} else if ("take_out".equals(helper.getType(c))) {icon.setImageResource(R.drawable.bg_video);}} catch(Exception e) {e.printStackTrace();}}}
}

当中用到两个xml文件：

<?xml version="1.0" encoding="utf-8"?>
<ListView xmlns:android="http://schemas.android.com/apk/res/android"android:id="@android:id/list"android:layout_width="fill_parent"android:layout_height="fill_parent"/>

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"android:layout_width="fill_parent"android:layout_height="wrap_content"android:orientation="horizontal"android:padding="4dip"><ImageView android:id="@+id/icon"android:layout_width="wrap_content"android:layout_height="fill_parent"android:layout_alignParentTop="true"android:layout_alignParentBottom="true"android:layout_marginRight="4dip"/><LinearLayoutandroid:layout_width="fill_parent"android:layout_height="wrap_content"android:orientation="vertical">  <TextView android:id="@+id/title"android:layout_width="fill_parent"android:layout_height="wrap_content"android:layout_weight="1"android:gravity="center_vertical"android:textStyle="bold"android:singleLine="true"android:ellipsize="end"/><TextView android:id="@+id/address"android:layout_width="fill_parent"android:layout_height="wrap_content"android:layout_weight="1"android:gravity="center_vertical"android:singleLine="true"android:ellipsize="end"/></LinearLayout>
</LinearLayout>

MainActivity类中主要是显示单项信息：

package com.example.activity_and_service;import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.database.Cursor;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.RadioGroup;
import android.widget.TextView;public class MainActivity extends Activity  {EditText name = null;EditText address = null;EditText notes = null;RadioGroup types = null;String restaurantId = null;RestaurantHelper helper = null;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);helper = new RestaurantHelper(this);name = (EditText)findViewById(R.id.name);address = (EditText)findViewById(R.id.addr);notes = (EditText)findViewById(R.id.notes);types = (RadioGroup)findViewById(R.id.types);Button save = (Button)findViewById(R.id.save);save.setOnClickListener(onSave);restaurantId = getIntent().getStringExtra(LunchList.ID_EXTRA);if (restaurantId != null) load();}public void onDestroy(){super.onDestroy();helper.close();}public void load(){Cursor c = helper.getById(restaurantId);c.moveToFirst();name.setText(helper.getName(c));address.setText(helper.getAddress(c));notes.setText(helper.getNotes(c));if ("sit_down".equals(helper.getType(c))) {types.check(R.id.sit_down);} else if ("take_out".equals(helper.getType(c))) {types.check(R.id.take_out);} else {types.check(R.id.delivery);}}private View.OnClickListener onSave = new View.OnClickListener() {@Overridepublic void onClick(View v) {// TODO Auto-generated method stubString type = null;switch(types.getCheckedRadioButtonId()) {case R.id.sit_down:type = "sit_down";break;case R.id.take_out:type = "take_out";break;case R.id.delivery:type = "delivery";break;}if (restaurantId == null) {helper.insert(name.getText().toString(), address.getText().toString(), type, notes.getText().toString());} else {helper.update(restaurantId, name.getText().toString(), address.getText().toString(), type, notes.getText().toString());}finish();}
};
}

其对应的xml文件：

<TableLayout xmlns:android="http://schemas.android.com/apk/res/android"android:layout_width="fill_parent"android:layout_height="wrap_content"android:stretchColumns="1"><TableRow><TextView android:text="Name:" /><EditText android:id="@+id/name" /></TableRow><TableRow><TextView android:text="Address:" /><EditText android:id="@+id/addr" /></TableRow><TableRow><TextView android:text="Type:" /><RadioGroup android:id="@+id/types"><RadioButton android:id="@+id/take_out"android:text="Take-Out"/><RadioButton android:id="@+id/sit_down"android:text="Sit-Down"/><RadioButton android:id="@+id/delivery"android:text="Delivery"/></RadioGroup></TableRow><TableRow><TextView android:text="Notes:" /><EditText android:id="@+id/notes"android:singleLine="false"android:gravity="top"android:lines="2"android:scrollHorizontally="false"android:maxLines="2"android:maxWidth="200sp"/></TableRow><Button android:id="@+id/save"android:layout_width="fill_parent"android:layout_height="wrap_content"android:text="Save"/>
</TableLayout>

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