初学_Android4高级编程-8 share preference&文件&状态保存

※使用share preference保存数据

SharedPreferences sharedPreferences = getSharedPreferences("setting", Activity.MODE_PRIVATE);

SharedPreferences.Editor editor = sharedPreferences.edit();

editor.putInt("int",1);

editor.putString("String","str");

editor.putBoolean("boolean",true);

//apply()异步保存，commit()同步保存

editor.commit();

sharedPreferences.getString("String","def");

sharedPreferences.getBoolean("boolean",false);

使用preferenceScreen

在xml文件夹中新建xml文件

<CheckBoxPreference
android:key="checkbox"
android:summary="男 ,女"
android:title="性别" />

<RingtonePreference
android:key="ringtone"
android:showDefault="true"
android:showSilent="true"
android:summary="Pick a tone, any tone"
android:title="Ringtone Preference" />

<ListPreference
android:entries="@array/my_array"
android:entryValues="@array/my_array"
android:key="list"
android:summary="select a list"
android:title="Type" />

<EditTextPreference
android:dialogTitle="nihao"
android:key="edit"
android:title="姓名" />

在Activity中添加布局文件并还原状态,继承PreferenceActivity。

addPreferencesFromResource(R.xml.preference_screen);

prefs= PreferenceManager.getDefaultSharedPreferences(this);

·使用saveInstanceState保存Activity,Fragment状态

@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setRetainInstance(true);
if(savedInstanceState != null){
userSelection = savedInstanceState.getInt(USER_SELECTION)
}
}
@Override
public void onSaveInstanceState(Bundle outState) {
outState.putInt(USER_SELECTION,userSelection);
super.onSaveInstanceState(outState);
}

※在文件中保存数据

·将文件保存到对应包名的目录下

String filename = "name.txt";

String str = "哈哈";

FileOutputStream fileOutputStream;

try {

fileOutputStream = openFileOutput(filename, Context.MODE_PRIVATE);

fileOutputStream.write(str.getBytes());

fileOutputStream.close();

} catch (Exception e) {

e.printStackTrace();

}

String ans = ReadTxtFile(this.getFilesDir() + "/" + filename);

Toast.makeText(this, ans.trim(), Toast.LENGTH_SHORT).show();

·读取对应目录下的文件输出字符内容

public String ReadTxtFile(String strFilePath) {

String path = strFilePath;

String content = ""; //文件内容字符串

//打开文件

File file = new File(path);

//如果path是传递过来的参数，可以做一个非目录的判断

if (file.isDirectory()) {

Toast.makeText(this, "文件不存在", Toast.LENGTH_SHORT).show();

} else {

try {

InputStream instream = new FileInputStream(file);

if (instream != null) {

InputStreamReader inputreader = new InputStreamReader(instream);

BufferedReader buffreader = new BufferedReader(inputreader);

String line;

//分行读取

while ((line = buffreader.readLine()) != null) {

content += line + "\n";

}

instream.close();

}

} catch (Exception e) {

Toast.makeText(this, "失败", Toast.LENGTH_SHORT).show();

}

}

return content;

}

·通过Environment.getExternalStorageDirectory()获取sd卡目录，保存文件到sd卡中，需要sd卡权限

File sdCardDir = Environment.getExternalStorageDirectory();

File file = new File(sdCardDir, filename);