ListView项目长按的菜单功能总结

ListView上的Item长按弹出菜单或者对话框是常见的功能之一：

其实现如下：

extends ListActivity{

在方法：

@Override

public void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

requestWindowFeature(Window.FEATURE_INDETERMINATE_PROGRESS);

setContentView(R.layout.localfilebrowser);

registerForContextMenu(this.getListView());

增加方法：

@Override
public void onCreateContextMenu(ContextMenu menu, View view,
ContextMenuInfo menuInfo) {
AdapterView.AdapterContextMenuInfo info;
try {
info = (AdapterView.AdapterContextMenuInfo) menuInfo;
} catch (ClassCastException e) {
Log.e("test", "bad menuInfo", e);
return;
}
currentPath = new File(paths.get(info.position));
showDialog(UPDATE_FILEPATH);

}

本文使用了弹出式窗口，如果是菜单的话，需要增加如下代码：

@Override
public boolean onContextItemSelected(MenuItem item) {
super.onContextItemSelected(item);
AdapterContextMenuInfo menuInfo = (AdapterContextMenuInfo) item
.getMenuInfo();
// Remember current selection
IconifiedTextListAdapter adapter = (IconifiedTextListAdapter) getListAdapter();
if (adapter == null) {
return false;
}
return true;
}

showDialog(UPDATE_FILEPATH);对应于如下代码：

@Override
protected Dialog onCreateDialog(int id) {
switch (id) {
case UPDATE_FILEPATH:
LayoutInflater inflater = LayoutInflater.from(this);
View view = inflater.inflate(R.layout.dialog_change_filepath, null);
final TextView oldet = (TextView) view.findViewById(R.id.oldfilepath);
final TextView newet = (TextView) view.findViewById(R.id.newfilepath);
prefs = PreferenceManager.getDefaultSharedPreferences(this);
oldet.setText(oldet.getText()+prefs.getString("CLB_DOWNLOAD_PATH", ""));
if(currentPath!=null)
newet.setText(newet.getText()+currentPath.getAbsolutePath());
return new AlertDialog.Builder(this).setIcon(
android.R.drawable.ic_dialog_alert).setTitle(
R.string.dialog_filepath).setView(view)
.setPositiveButton(android.R.string.ok,
new OnClickListener() {
public void onClick(DialogInterface dialog,
int which) {
Editor editor = prefs.edit();
editor.putString("CLB_DOWNLOAD_PATH", currentPath.getAbsolutePath());
editor.commit();
ListOSDir.this.finish();
}
}).setNegativeButton(android.R.string.cancel,
new OnClickListener() {
public void onClick(DialogInterface dialog,
int which) {
// Cancel should not do anything.
removeDialog(UPDATE_FILEPATH);
}
}).create();
}
return null;
}

其中：removeDialog(UPDATE_FILEPATH);
是解决

因为create 一个dialog的开销很大，所以android会先查找有没有dialog实例存在，如果有，不create，prepared之后就show，弹出窗口一直都相同的问题

整个程序是选择一个目录来设置下载需要存储的路径的，代码如下：

package cn.cnic.cerc.moblie.clbclient.filemanager;
import java.io.File;
import java.util.ArrayList;
import java.util.List;
import android.app.AlertDialog;
import android.app.Dialog;
import android.app.ListActivity;
import android.content.DialogInterface;
import android.content.SharedPreferences;
import android.content.DialogInterface.OnClickListener;
import android.content.SharedPreferences.Editor;
import android.os.Bundle;
import android.os.Environment;
import android.preference.PreferenceManager;
import android.util.Log;
import android.view.ContextMenu;
import android.view.LayoutInflater;
import android.view.MenuItem;
import android.view.View;
import android.view.Window;
import android.view.ContextMenu.ContextMenuInfo;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import android.widget.TextView;
import android.widget.AdapterView.AdapterContextMenuInfo;
import cn.cnic.cerc.moblie.clbclient.R;
public class ListOSDir extends ListActivity {
private static final int UPDATE_FILEPATH = 0;
/** Called when the activity is first created. */
private List<String> items = null;// 存放名称
private List<String> paths = null;// 存放路径
private String rootPath = "/";
private TextView tv;
private SharedPreferences prefs;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
requestWindowFeature(Window.FEATURE_INDETERMINATE_PROGRESS);
setContentView(R.layout.localfilebrowser);
registerForContextMenu(this.getListView());
tv = (TextView) this.findViewById(R.id.TextView);
this.getFileDir(rootPath);// 获取rootPath目录下的文件.
prefs = PreferenceManager.getDefaultSharedPreferences(this);
if(prefs.getString("CLB_DOWNLOAD_PATH", "").equals(""))
{
File sdcardDir = Environment.getExternalStorageDirectory();
String path = sdcardDir.getParent() + sdcardDir.getName();
String fileDirectory = path + java.io.File.separator + "clb";
Editor editor = prefs.edit();
editor.putString("CLB_DOWNLOAD_PATH", fileDirectory);
editor.commit();
}
}
public void getFileDir(String filePath) {
try {
this.tv.setText("当前路径:" + filePath);// 设置当前所在路径
items = new ArrayList<String>();
paths = new ArrayList<String>();
File f = new File(filePath);
File[] files = f.listFiles();// 列出所有文件
// 如果不是根目录,则列出返回根目录和上一目录选项
if (!filePath.equals(rootPath)) {
items.add("返回根目录");
paths.add(rootPath);
items.add("返回上一层目录");
paths.add(f.getParent());
}
// 将所有文件存入list中
if (files != null) {
int count = files.length;// 文件个数
for (int i = 0; i < count; i++) {
File file = files[i];
if (file.isDirectory()) {
items.add(file.getName());
paths.add(file.getPath());
}
}
}
ArrayAdapter<String> adapter = new ArrayAdapter<String>(this,
android.R.layout.simple_list_item_1, items);
this.setListAdapter(adapter);
} catch (Exception ex) {
ex.printStackTrace();
}
}
@Override
protected void onListItemClick(ListView l, View v, int position, long id) {
super.onListItemClick(l, v, position, id);
String path = paths.get(position);
File file = new File(path);
// 如果是文件夹就继续分解
if (file.isDirectory()) {
this.getFileDir(path);
} else {
new AlertDialog.Builder(this).setTitle("提示").setMessage(
file.getName() + " 是一个文件！").setPositiveButton("OK",
new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int which) {
}
}).show();
}
}
private File currentPath;
@Override
public void onCreateContextMenu(ContextMenu menu, View view,
ContextMenuInfo menuInfo) {
AdapterView.AdapterContextMenuInfo info;
try {
info = (AdapterView.AdapterContextMenuInfo) menuInfo;
} catch (ClassCastException e) {
Log.e("test", "bad menuInfo", e);
return;
}
currentPath = new File(paths.get(info.position));
showDialog(UPDATE_FILEPATH);

}
@Override
public boolean onContextItemSelected(MenuItem item) {
super.onContextItemSelected(item);
AdapterContextMenuInfo menuInfo = (AdapterContextMenuInfo) item
.getMenuInfo();
// Remember current selection
IconifiedTextListAdapter adapter = (IconifiedTextListAdapter) getListAdapter();
if (adapter == null) {
return false;
}
return true;
}

@Override
protected Dialog onCreateDialog(int id) {
switch (id) {
case UPDATE_FILEPATH:
LayoutInflater inflater = LayoutInflater.from(this);
View view = inflater.inflate(R.layout.dialog_change_filepath, null);
final TextView oldet = (TextView) view.findViewById(R.id.oldfilepath);
final TextView newet = (TextView) view.findViewById(R.id.newfilepath);
prefs = PreferenceManager.getDefaultSharedPreferences(this);
oldet.setText(oldet.getText()+prefs.getString("CLB_DOWNLOAD_PATH", ""));
if(currentPath!=null)
newet.setText(newet.getText()+currentPath.getAbsolutePath());
return new AlertDialog.Builder(this).setIcon(
android.R.drawable.ic_dialog_alert).setTitle(
R.string.dialog_filepath).setView(view)
.setPositiveButton(android.R.string.ok,
new OnClickListener() {
public void onClick(DialogInterface dialog,
int which) {
Editor editor = prefs.edit();
editor.putString("CLB_DOWNLOAD_PATH", currentPath.getAbsolutePath());
editor.commit();
ListOSDir.this.finish();
}
}).setNegativeButton(android.R.string.cancel,
new OnClickListener() {
public void onClick(DialogInterface dialog,
int which) {
// Cancel should not do anything.
removeDialog(UPDATE_FILEPATH);
}
}).create();
}
return null;
}

}