Android数据存储方式之：文件存储

来源：互联网发布：杭州边锋网络怎么样编辑：程序博客网时间：2024/05/18 09:15

android应用大多数用的java开发，所以java的文件操作在android中完全适用，只不过android对手机而言，多了个外存储设置SD卡。

----------------------------------------------简单的界面布局-----------------------------------------------------------

-----------------------------功能代码-----------------------------------------------------------

public class MainActivity extends Activity implements OnClickListener {
/**内容输入框 */
private EditText inputEdt;
/**保存(写入)按钮 */
private Button writeBtn;
/**读取按钮 */
private Button readBtn;
/**要保存的文件名*/
private static final String FILE_NAME = "temp_file.txt";

@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
findViewsById();
}

private void findViewsById() {
inputEdt = (EditText) findViewById(R.id.input_edt);
writeBtn = (Button) findViewById(R.id.write_btn);
readBtn = (Button) findViewById(R.id.read_btn);
writeBtn.setOnClickListener(this);
readBtn.setOnClickListener(this);
}

@Override
public void onClick(View v) {
switch (v.getId()) {
case R.id.write_btn:
writeData();
break;
case R.id.read_btn:
String result = readData();
inputEdt.setText(result);
break;
}
}

/*
* 方法openFileOutput(FILE_NAME, Activity.MODE_PRIVATE); 参数说明：以FILE_NAME文件名，Activity.MODE_PRIVATE文件的应用模式，打开一个输出流如果文件不存系统会为你创建一个注意这里的文件名称不能包括任何的/或者/这种分隔符，只能是文件名
* 该文件会被保存在/data/data/应用名称/files/temp_file.txt 文件的操作模式有以下四种：MODE_PRIVATE 私有（只能创建它的应用访问）重复写入时会文件覆盖MODE_APPEND 私有重复写入时会在文件的末尾进行追加，而不是覆盖掉原来的文件 MODE_WORLD_READABLE 公用可读 MODE_WORLD_WRITEABLE 公用可读写
*/
private void writeData() {
String content = inputEdt.getText().toString();
try {

FileOutputStream outputStream = openFileOutput(FILE_NAME, Activity.MODE_PRIVATE);
outputStream.write(content.getBytes());
outputStream.flush();
outputStream.close();
Toast.makeText(MainActivity.this, "保存成功", Toast.LENGTH_LONG).show();
} catch (Exception e) {
e.printStackTrace();
}
}

/**
* 把刚刚保存的数据读出来
* */
private String readData() {
String content = "";
try {
FileInputStream inputStream = this.openFileInput(FILE_NAME);
byte[] bytes = new byte[1024];
ByteArrayOutputStream arrayOutputStream = new ByteArrayOutputStream();
while (inputStream.read(bytes) != -1) {
arrayOutputStream.write(bytes, 0, bytes.length);
}
inputStream.close();
arrayOutputStream.close();
content = new String(arrayOutputStream.toByteArray());

} catch (Exception e) {
e.printStackTrace();
}
return content;

}

/****************上面的内容是把内容存到手机内存中*************************************/
/**判断SDcard是否存在并且可读写*/

private boolean isSDcardExist() {

if (Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)) {
return true;
} else {
Toast.makeText(getApplicationContext(), "内存卡不可用", 1000).show();
return false;
}
}

/**往内存卡中存文件*/
public void writeToSDCard(String filename, String filecontent) throws Exception {
File file = new File(Environment.getExternalStorageDirectory(), filename);
FileOutputStream outStream = new FileOutputStream(file);
outStream.write(filecontent.getBytes());
outStream.close();
}

/**读SD卡中对应文件的内容*/
private String readSDCardFile(String filePath, String fileName) {
String result = "";
try {
File file = new File(filePath, fileName);
FileInputStream is = new FileInputStream(file);
byte[] b = new byte[is.available()];
is.read(b);
result = new String(b);
} catch (Exception e) {
e.printStackTrace();
}
return result;
}

}

---------注：-------------------------------------------

SD卡操作不要忘记在AndroidManifest.xml中添加对应权限：

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
<uses-permission android:name="android.permission.MOUNT_UNMOUNT_FILESYSTEMS"/>

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