Android应用开发之多选删除之二

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MultiSelectDeleteActivity.java

package cn.lynn.multisel;

import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;

import android.app.Activity;
import android.app.AlertDialog;
import android.app.ProgressDialog;
import android.content.ContentUris;
import android.content.Context;
import android.content.DialogInterface;
import android.database.Cursor;
import android.net.Uri;
import android.os.AsyncTask;
import android.os.Bundle;
import android.provider.ContactsContract.Contacts;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.BaseAdapter;
import android.widget.Button;
import android.widget.CheckBox;
import android.widget.ListView;
import android.widget.TextView;

public class MultiSelectDeleteActivity extends Activity implements OnClickListener, OnItemClickListener {

    private static final String TAG = "MultiSelectDeleteActivity";
    private ListView delList;
    private Button delBtn;
    private Button canBtn;
    private CheckBox selAllChk;
    private Cursor cursor;
    private int count;
    private DeleteListAdapter delListAdapter;
    // 期望查询的联系人字段
    private static final String[] PROJECTION = new String[] {Contacts._ID, Contacts.DISPLAY_NAME};
    private static final int CONTACTS_ID_INDEX = 0;
    private static final int DISPLAY_NAME_INDEX = 1;
    
    // 用于保存记录是否被选中的状态，这里定义为静态变量是为了防止Home键切换之后普通成员变量无法保存切换之前的数据
    private static HashMap<Integer, Boolean> statusMap;

    /**
     * 用于删除的联系人记录的封装类
     */
    private final class ViewHolder {
        TextView nameTxt;
        CheckBox selectChk;
    }
    
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        
        statusMap = new HashMap<Integer, Boolean>();

        delList = (ListView) findViewById(R.id.del_list);
        delBtn = (Button) findViewById(R.id.del_btn);
        canBtn = (Button) findViewById(R.id.can_btn);
        selAllChk = (CheckBox) findViewById(R.id.select_all).findViewById(R.id.select_all_chk);
        
        delList.setOnItemClickListener(this);
        delBtn.setOnClickListener(this);
        canBtn.setOnClickListener(this);
        selAllChk.setOnClickListener(new SelectAllClickListener());
    }
    
    @Override
    protected void onDestroy() {
        super.onDestroy();
        statusMap.clear();
        // 静态变量，提示和加快GC回收它，否则有很大可能要等到VM Full gc时才能回收
        statusMap = null;
    }
    
    @Override
    public void onResume() {
        super.onResume();
        refreshData();
    }
    
    @Override
    protected void onPause() {
        super.onPause();
        // 保存切换之前的记录数
        count = cursor.getCount();
    }

    /**
     * 查询联系人数据库记录
     */
    private void refreshData() {
        selAllChk.setEnabled(false);
        delBtn.setEnabled(false);
        cursor = getContentResolver().query(Contacts.CONTENT_URI, PROJECTION, null, null, null);
        if(cursor.getCount() > 0) {
            selAllChk.setEnabled(true);
            // Home键切换到Contacts应用增加联系人
            if(count < cursor.getCount()) {
                selAllChk.setChecked(false);
            }
        }
        if(statusMap.containsValue(true)) {
            delBtn.setEnabled(true);
        }
        Log.i(TAG, "cursor= " + cursor);
        delListAdapter = new DeleteListAdapter(this, cursor);
        delList.setAdapter(delListAdapter);
        delListAdapter.notifyDataSetChanged();
    }
    
    /**
     * 单独为全选CheckBox设置点击事件的监听器，因为它的布局是从当前Activity的子布局文件R.id.select_all中加载而来，
     * 这样做的好处是防止多个按钮都在Activity布局层次上监听同类点击事件时出现“屏蔽”现象
     */
    private class SelectAllClickListener implements OnClickListener {
        @Override
        public void onClick(View v) {
            if(selAllChk.isChecked()) {
                for (int i = 0; i < delListAdapter.getCount(); i++) {
                    statusMap.put(i, true);
                    delListAdapter.cursor.moveToPosition(i);
                    delListAdapter.idSet.add(delListAdapter.cursor.getInt(CONTACTS_ID_INDEX) + "");
                }
                delBtn.setEnabled(true);
            } else {
                for (int i = 0; i < delListAdapter.getCount(); i++) {
                    statusMap.put(i, false);
                }
                delListAdapter.idSet.clear();
                delBtn.setEnabled(false);
            }
            // 数据发生变化，通知UI更新
            delListAdapter.notifyDataSetChanged();
        }
        
    }

    /**
     * 为ListView设置删除联系人记录的Adapter
     */
    private class DeleteListAdapter extends BaseAdapter {
        Cursor cursor;
        // 保存被选中的联系人Id
        HashSet<String> idSet;
        
        public DeleteListAdapter(Context context, Cursor cursor) {
            this.cursor = cursor;
            idSet = new HashSet<String>();
            for (int i = 0; i < cursor.getCount(); i++) {
                // 初始化新的联系人记录为未选中的状态
                if(statusMap.containsKey(i)) continue;
                statusMap.put(i, false);
            }
            Log.i(TAG, "statusMap size=" + statusMap.size());
        }

        @Override
        public int getCount() {
            return cursor.getCount();
        }

        @Override
        public Object getItem(int position) {
            if(cursor.moveToPosition(position)) {
                return cursor;
            } else {
                return null;
            }
        }

        @Override
        public long getItemId(int position) {
            return position;
        }

        // 这里启用了convertView缓存，并创建ViewHolder类以提高ListView执行效率
        @Override
        public View getView(int position, View convertView, ViewGroup parent) {
            ViewHolder holder = null;
            if(convertView == null) {
                convertView = LayoutInflater.from(MultiSelectDeleteActivity.this).inflate(R.layout.list_item, null);
                holder = new ViewHolder();
                holder.nameTxt = (TextView) convertView.findViewById(R.id.name_txt);
                holder.selectChk = (CheckBox) convertView.findViewById(R.id.select_chk);
                convertView.setTag(holder);
            }
            cursor.moveToPosition(position);
            holder = (ViewHolder) convertView.getTag();
            final String name = cursor.getString(DISPLAY_NAME_INDEX);
            holder.nameTxt.setText(name);
            holder.selectChk.setChecked(statusMap.get(position));
            if(statusMap.get(position)) {
                // 存储选中状态的记录的Id
                idSet.add(cursor.getInt(CONTACTS_ID_INDEX)+"");
            } else {
                // 移除非选中状态的记录的Id
                idSet.remove(cursor.getInt(CONTACTS_ID_INDEX)+"");
            }
            return convertView;
        }
    }

    @Override
    public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
        Log.i(TAG, "onItemClick...");
        ViewHolder holder = (ViewHolder) view.getTag();
        holder.selectChk.toggle();
        statusMap.put(position, holder.selectChk.isChecked());
        delListAdapter.notifyDataSetChanged();
        // 判断是否有记录没被选中，以便更改全选CheckBox的勾选状态
        if(statusMap.containsValue(false)) {
            selAllChk.setChecked(false);
        } else {
            selAllChk.setChecked(true);
        }
        Log.i(TAG, "------------statusMap data--------------");
        for (Map.Entry<Integer, Boolean> entry: statusMap.entrySet()) {
            Log.i(TAG, "statusMap key=" + entry.getKey() + ", value= " + entry.getValue());
        }
        
        // 判断是否有记录被选中，以便更改删除Button的可用状态
        if(statusMap.containsValue(true)) {
            delBtn.setEnabled(true);
        } else {
            delBtn.setEnabled(false);
        }
    }

    @Override
    public void onClick(View v) {
        switch (v.getId()) {
        // 删除按钮
        case R.id.del_btn:
            new AlertDialog.Builder(this)
                .setTitle(R.string.clearConfirmation_title)
                .setMessage(R.string.clearConfirmation)
                .setNegativeButton(android.R.string.cancel, null)
                .setPositiveButton(android.R.string.ok, new DialogInterface.OnClickListener() {
                    @SuppressWarnings("unchecked")
                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                        final ProgressDialog progressDialog = ProgressDialog.show(MultiSelectDeleteActivity.this, getString(R.string.clearProgress_title), "", true, false);
                        final AsyncTask<HashSet<String>, Integer, Cursor> deleteWork = new AsyncTask<HashSet<String>, Integer, Cursor>() {
                            Uri uri = null;
                            @Override
                            protected Cursor doInBackground(HashSet<String> ... params) {
                                // 后台工作线程执行删除联系人记录操作
                                HashSet<String> ids = params[0];
                                for (String id : ids) {
                                    Log.i(TAG, "deleted id= " + id);
                                    uri = ContentUris.withAppendedId(Contacts.CONTENT_URI, Long.valueOf(id));
                                    MultiSelectDeleteActivity.this.getContentResolver().delete(uri, null, null);
                                }
                                Log.i(TAG, "doInBackground statusMap size=" + statusMap.size());
                                // 清除所有被选中的联系人Id
                                delListAdapter.idSet.clear();
                                cursor = MultiSelectDeleteActivity.this.getContentResolver().query(Contacts.CONTENT_URI, PROJECTION, null, null, null);
                                return cursor;
                            }
                            
                            // 删除操作的实时进度，本案例不对此做任何处理
                            @Override
                            protected void onProgressUpdate(Integer... values) {
                                super.onProgressUpdate(values);
                            }
                            
                            // 删除操作执行完毕后回调此方法，可以得到处理结果，并通知UI更新
                            @Override
                            protected void onPostExecute(Cursor result) {
                                super.onPostExecute(result);
                                Log.i(TAG, "result getCount= " + result.getCount());
                                if(result.getCount() == 0){
                                    // 删除全部记录后，全选CheckBox应该被禁用（不能再点击），当有新记录加入时才可以重新启用它
                                    selAllChk.setChecked(false);
                                    selAllChk.setEnabled(false);
                                }
                                delBtn.setEnabled(false);
                                statusMap.clear();
                                // 删除操作完成后，重置剩下的记录为未选中状态
                                for (int i = 0; i < result.getCount(); i++) {
                                    statusMap.put(i, false);
                                }
                                delListAdapter.cursor = result;
                                delListAdapter.notifyDataSetChanged();
                                progressDialog.dismiss();
                            }
                        };
                        progressDialog.show();
                        deleteWork.execute(delListAdapter.idSet);
                    }
                })
                .setCancelable(true)
                .create()
                .show();
            break;
            
         // 取消按钮
        case R.id.can_btn:
            
            break;
        }
    }
}

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