在实际的开发中，Android提供了5种数据存储的方式：
1）文件存储数据
2）使用SharedPreferences存储数据
3）使用SQLite数据库存储数据
4）使用ContentProvide存储数据
5）网络存储数据
一、文件存储数据到内部存储器
1）为了保存文本到文件中，需要FileOutputStream类，openFileOutput方法用指定的模式打开一个指定的文件夹来写入：
FileOutputStream fileOut = openFileOutput(“hello.txt”, Context.MODE_WORLD_WRITEABLE);
其中，有三种模式提供选择：
Context.MODE_PRIVATE: 创建的文件只能被该应用程序读写
Context.MODE_WORLD_READABLE:允许其他应用程序读取文件
Context.MODE_WORLD_WRITEABLE: 允许其他应用程序修改文件
2）为了将字符流转换为字节流，需要OutputStreamWriter类的对象，并传入FileOutputStream类的实例作为参数：
OutputStreamWriter osw = newOutputStreamWriter(fileOut);
3）而读取文件则需要用到FileInputStream类和InputStreamReader类：
FileInputStream fileInput = openFileInput(“hello.txt”);
InputStreamReader isr = new InputStreamReader(fileInput);
4）新建一个字符数组作为缓冲器，把文件内容读到缓冲器中，然后将其复制到String对象中
char[] inputBuffer = new char[READ_BLOCK_SIZE];
String s = “”;
int charRead;
while((charRead = isr.read(inputBuffer)>0){
StringreadString = String.copyValueOf(inputBuffer, 0, charRead);
s +=readString;
inputBuffer= new char[READ_BLOCK_SIZE];
}
public class FilesActivity extends Activity {
EditText textBox;
static final int READ_BLOCK_SIZE = 100;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
this.textBox = (EditText)findViewById(R.id.txtText);
}
public void onClickSave(View v){
String str = textBox.getText().toString();
try {
FileOutputStream fileOut = openFileOutput("hello.txt", MODE_WORLD_READABLE);
OutputStreamWriter osw = new OutputStreamWriter(fileOut);
osw.write(str);
osw.flush();
osw.close();
Toast.makeText(getBaseContext(), "File saved successfully!",
Toast.LENGTH_SHORT).show();
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
public void onClickLoad(View v){
try {
FileInputStream fileInput = openFileInput("hello.txt");
InputStreamReader isr = new InputStreamReader(fileInput);
char[] inputBuffer = new char[READ_BLOCK_SIZE];
String s = "";
int charRead;
while((charRead = isr.read(inputBuffer)) > 0){
String readString = String.copyValueOf(inputBuffer, 0, charRead);
s += readString;
inputBuffer = new char[READ_BLOCK_SIZE];
}
textBox.setText(s);
Toast.makeText(getBaseContext(), "File loaded successfully",
Toast.LENGTH_SHORT).show();
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
二、文件存储数据到SD卡
返回sd卡的完整路径：
File sdCard = Environment.getExternalStorageDirectory();
在SD卡中创建一个名问MyFiles的目录，最终文件将会保存到这里：
File directory = new File(sdCard.getAbsolutePath()+"/MyFiles");
directory.mkdir();
读取SD卡需要在AndroidMinifest.xml文件中添加权限：
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE">
</uses-permission>
其他的跟上面的一样,下面看代码：
public class FilesActivity extends Activity {
EditText textBox;
static final int READ_BLOCK_SIZE = 100;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
this.textBox = (EditText)findViewById(R.id.txtText);
}
public void onClickSave(View v){
String str = textBox.getText().toString();
try {
File sdCard = Environment.getExternalStorageDirectory();//返回sd卡的路径
File directory = new File(sdCard.getAbsolutePath()+"/MyFiles");
directory.mkdir();
File file = new File(directory, "textfile.txt");
FileOutputStream fileOut = new FileOutputStream(file);
OutputStreamWriter osw = new OutputStreamWriter(fileOut);
osw.write(str);
osw.flush();
osw.close();
Toast.makeText(getBaseContext(), "File saved successfully!",
Toast.LENGTH_SHORT).show();
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
public void onClickLoad(View v){
try {
File sdCard = Environment.getExternalStorageDirectory();
File directory = new File(sdCard.getAbsolutePath()+"/MyFiles");
File file = new File(directory, "textfile.txt");
FileInputStream fileIn;
fileIn = new FileInputStream(file);
InputStreamReader isr = new InputStreamReader(fileIn);
char[] inputBuffer = new char[READ_BLOCK_SIZE];
String s = "";
int charRead;
while((charRead = isr.read(inputBuffer)) > 0){
String readString = String.copyValueOf(inputBuffer, 0, charRead);
s += readString;
inputBuffer = new char[READ_BLOCK_SIZE];
}
textBox.setText(s);
Toast.makeText(getBaseContext(), "File loaded successfully",
Toast.LENGTH_SHORT).show();
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
二、使用SharedPreferences存储数据
【存】
创建对象：
SharedPreferences sp = getSharedPreferences("FILE_NAME",MODE_PRIVATE);
创建编辑器：
SharedPreferences.Editor editor = sp.edit();
往编辑器存入int、boolean、String等类型的数据分别使用对应的方法：
editor.putBoolean("flag", true);
editor.putInt("age", 40);
editor.putString("你好啊，请多多指教","message");
编辑器必须发送出去才能生效：
editor.commit();
【取】
还是需要SharedPreferences 对象：
SharedPreferences sp =getSharedPreferences("FILE_NAME",MODE_PRIVATE);
与set对应，取出对应的数据是get，如getBoolean、getString等：
booleanflag = sp.getBoolean("flag",false);
int age =sp.getInt("age", 0);
String mess = sp.getString("message","No message");
public class MainActivity extends Activity {
private Button send,look;
private EditText input;
private TextView msg;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
this.msg = (TextView)findViewById(R.id.msg);
this.send = (Button)findViewById(R.id.send);
this.look = (Button)findViewById(R.id.look);
this.input = (EditText)findViewById(R.id.input);
send.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
SharedPreferences sp = getSharedPreferences("FILE_NAME", MODE_PRIVATE);
SharedPreferences.Editor editor = sp.edit();
editor.putString("message",input.getText().toString());
editor.commit();
msg.setText("你有新的消息，请注意查收");
}
});
look.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
SharedPreferences sp = getSharedPreferences("FILE_NAME", MODE_PRIVATE);
String mess = sp.getString("message", "No message");
msg.setText(mess);
}
});
}
}
三、使用静态资源
也就是使用在res/raw文件夹下的文件。使用Activity类的getResources方法返回一个Resources对象，然后使用其openRawResource方法打开包含在res/raw文件夹下的文件。
public void onClickGetSources(View v){
InputStream is = getBaseContext().getResources().openRawResource(R.raw.text);
BufferedReader br = new BufferedReader(new InputStreamReader(is));
String str = null;
try {
while((str = br.readLine())!=null){
Toast.makeText(getBaseContext(), str, Toast.LENGTH_SHORT).show();
}
is.close();
br.close();
} catch (IOException e) {
e.printStackTrace();
}
}