Android使用文件存储数据

Android上最基本的存储数据的方式即为使用文件存储数据，使用基本的Java的FileOutStream,BufferedWriter,FileInputStream和BufferedReader即可。

MainActivity.java

package org.elvalad.filepersistencetest;
 
import android.app.Activity;
import android.content.Context;
import android.os.Bundle;
import android.text.TextUtils;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.EditText;
import android.widget.Toast;
 
import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
 
public class MainActivity extends Activity {
    private EditText edit;
 
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        edit = (EditText) findViewById(R.id.edit);
        String inputText = load();
        if (!TextUtils.isEmpty(inputText)) {
            edit.setText(inputText);
            edit.setSelection(inputText.length());
            Toast.makeText(MainActivity.this, "Restoring successed", Toast.LENGTH_SHORT).show();
        }
    }
 
    @Override
    protected void onDestroy() {
        super.onDestroy();
        String inputText = edit.getText().toString();
        save(inputText);
    }
 
    public void save(String inputText) {
        FileOutputStream out = null;
        BufferedWriter writer = null;
        try {
            out = openFileOutput("data", Context.MODE_APPEND);
            writer = new BufferedWriter(new OutputStreamWriter(out));
            writer.write(inputText);
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                if (writer != null) {
                    writer.close();
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
 
    public String load() {
        FileInputStream in = null;
        BufferedReader reader = null;
        StringBuilder content = new StringBuilder();
        try {
            in = openFileInput("data");
            reader = new BufferedReader(new InputStreamReader(in));
            String line = "";
            while ((line = reader.readLine()) != null) {
                content.append(line);
            }
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            if (reader != null) {
                try {
                    reader.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
        return content.toString();
    }
 
    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_main, menu);
        return true;
    }
 
    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();
 
        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }
 
        return super.onOptionsItemSelected(item);
    }
}

activity_main.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:orientation="horizontal"
    tools:context=".MainActivity">
 
    <EditText
        android:id="@+id/edit"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:hint="Type something here"/>
 
</LinearLayout>