File数据存储

把数据保存到文件中

从文件中读取数据

package com.gao.filesave;

import android.content.Context;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.text.TextUtils;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;

/**
* 文件存储
*/
public class MainActivity extends AppCompatActivity {

EditText mEditText;
Button mButton,save;

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

mEditText = (EditText) findViewById(R.id.input);
mButton = (Button) findViewById(R.id.button);
save = (Button) findViewById(R.id.button2);

save.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
String text = mEditText.getText().toString();
if (!TextUtils.isEmpty(text)){
save(text);
mEditText.setText("");
}else {
Toast.makeText(MainActivity.this, "保存数据为空", Toast.LENGTH_SHORT).show();
}

}
});
mButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
//从文件中读取文本数据
String inputText = load();

if (!TextUtils.isEmpty(inputText)) {
mEditText.setText(inputText);

//调用 setSelection 方法将输入光标移动到文本的末尾位置以便于继续输入
mEditText.setSelection(inputText.length());
Toast.makeText(MainActivity.this, "成功回现数据", Toast.LENGTH_SHORT).show();
}
}
});

}

/**
* //从文件中读取文本数据的方法
*
* @return
*/
private String load() {

FileInputStream fis = null;
BufferedReader bufferedReader = null;
StringBuilder content = new StringBuilder();

try {
//先通过 openFileInput()方法获取到了一个 FileInputStream 对象
fis = openFileInput("data");

//再 构建出了一个 InputStreamReader对象
bufferedReader = new BufferedReader(new InputStreamReader(fis));

String line = "";
while ((line = bufferedReader.readLine()) != null) {
content.append(line);

}

} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} finally {
if (bufferedReader != null) {
try {
bufferedReader.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
return content.toString();
}

@Override
protected void onDestroy() {
super.onDestroy();

String text = mEditText.getText().toString();
save(text);

}
//将文本内容写入到文件中

/**
* 保存数据的方法
*
* @param input 输入的内容
*/
private void save(String input) {
FileOutputStream out = null;
BufferedWriter bufferedWriter = null;

try {
//通过 openFileOutput()方法能够得到一个 FileOutputStream 对象
out = openFileOutput("data", Context.MODE_PRIVATE);

//然后再构建出一个 OutputStreamWriter 对象
bufferedWriter = new BufferedWriter(new OutputStreamWriter(out));

bufferedWriter.write(input); //通过 BufferedWriter 来将文本内容写入到文件中

} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} finally {
if (bufferedWriter != null) {
try {
bufferedWriter.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}

}