android自带musicplayer源码分析：RenamePlaylist类

package com.android.music; import android.app.Activity; ... public class RenamePlaylist extends Activity { private EditText mPlaylist; private TextView mPrompt; private Button mSaveButton; private long mRenameId; private String mOriginalName; @Override public void onCreate(Bundle icicle) { super.onCreate(icicle); setVolumeControlStream(AudioManager.STREAM_MUSIC); //设定音频控制为music requestWindowFeature(Window.FEATURE_NO_TITLE); //设定基本窗口属性和视图 setContentView(R.layout.create_playlist); getWindow().setLayout(WindowManager.LayoutParams.MATCH_PARENT, WindowManager.LayoutParams.WRAP_CONTENT); mPrompt = (TextView)findViewById(R.id.prompt); mPlaylist = (EditText)findViewById(R.id.playlist); mSaveButton = (Button) findViewById(R.id.create); mSaveButton.setOnClickListener(mOpenClicked); //设定保存按钮的click监听器 //设定点击取消按钮时finish此activity ((Button)findViewById(R.id.cancel)).setOnClickListener(new View.OnClickListener() { public void onClick(View v) { finish(); } }); //从此activity的caller传递的bundle中或者启动activity的intent中获得需要重命名的播放列表的id mRenameId = icicle != null ? icicle.getLong("rename") : getIntent().getLongExtra("rename", -1); //通过id获得此播放列表的旧名称 mOriginalName = nameForId(mRenameId); String defaultname = icicle != null ? icicle.getString("defaultname") : mOriginalName; //若获取失败则退出此activity if (mRenameId < 0 || mOriginalName == null || defaultname == null) { Log.i("@@@@", "Rename failed: " + mRenameId + "/" + defaultname); finish(); return; } String promptformat; if (mOriginalName.equals(defaultname)) { promptformat = getString(R.string.rename_playlist_same_prompt); } else { promptformat = getString(R.string.rename_playlist_diff_prompt); } String prompt = String.format(promptformat, mOriginalName, defaultname); mPrompt.setText(prompt); mPlaylist.setText(defaultname); mPlaylist.setSelection(defaultname.length()); mPlaylist.addTextChangedListener(mTextWatcher); //设置edittext更新的监听器 setSaveButton(); } TextWatcher mTextWatcher = new TextWatcher() { public void beforeTextChanged(CharSequence s, int start, int count, int after) { // don't care about this one } public void onTextChanged(CharSequence s, int start, int before, int count) { // check if playlist with current name exists already, and warn the user if so. setSaveButton(); }; public void afterTextChanged(Editable s) { // don't care about this one } }; private void setSaveButton() { String typedname = mPlaylist.getText().toString(); //若内容为空则将按钮设为不可用 if (typedname.trim().length() == 0) { mSaveButton.setEnabled(false); } else { mSaveButton.setEnabled(true); //如果此名称已存在或者和旧名称一样，则按钮显示为覆盖，不然显示为创建 if (idForplaylist(typedname) >= 0 && ! mOriginalName.equals(typedname)) { mSaveButton.setText(R.string.create_playlist_overwrite_text); } else { mSaveButton.setText(R.string.create_playlist_create_text); } } } //查询播放列表数据库中NAME ＝ name的记录并返回此项的id值，若没有则返回－1 //详细分析见CreatePlaylist类的分析 private int idForplaylist(String name) { Cursor c = MusicUtils.query(this, MediaStore.Audio.Playlists.EXTERNAL_CONTENT_URI, new String[] { MediaStore.Audio.Playlists._ID }, MediaStore.Audio.Playlists.NAME + "=?", new String[] { name }, MediaStore.Audio.Playlists.NAME); int id = -1; if (c != null) { c.moveToFirst(); if (!c.isAfterLast()) { id = c.getInt(0); } } c.close(); return id; } //通过id值来查询播放列表的名称 private String nameForId(long id) { Cursor c = MusicUtils.query(this, MediaStore.Audio.Playlists.EXTERNAL_CONTENT_URI, new String[] { MediaStore.Audio.Playlists.NAME }, MediaStore.Audio.Playlists._ID + "=?", new String[] { Long.valueOf(id).toString() }, MediaStore.Audio.Playlists.NAME); String name = null; if (c != null) { c.moveToFirst(); if (!c.isAfterLast()) { name = c.getString(0); } } c.close(); return name; } @Override public void onSaveInstanceState(Bundle outcicle) { outcicle.putString("defaultname", mPlaylist.getText().toString()); outcicle.putLong("rename", mRenameId); } @Override public void onResume() { super.onResume(); } private View.OnClickListener mOpenClicked = new View.OnClickListener() { public void onClick(View v) { String name = mPlaylist.getText().toString(); if (name != null && name.length() > 0) { ContentResolver resolver = getContentResolver(); ContentValues values = new ContentValues(1); values.put(MediaStore.Audio.Playlists.NAME, name); //使用update方法更新_ID值等于mRenameId的记录的NAME项 resolver.update(MediaStore.Audio.Playlists.EXTERNAL_CONTENT_URI, values, MediaStore.Audio.Playlists._ID + "=?", new String[] { Long.valueOf(mRenameId).toString()}); //返回一个RESULT_OK消息 setResult(RESULT_OK); //显示一个重命名成功的toast提示框 Toast.makeText(RenamePlaylist.this, R.string.playlist_renamed_message, Toast.LENGTH_SHORT).show(); finish(); } } }; }