IO流最简易用法demo

import android.support.v7.app.AppCompatActivity;import android.os.Bundle;import android.view.View;import android.widget.EditText;import android.widget.TextView;import java.io.FileInputStream;import java.io.FileOutputStream;import java.io.PrintStream;public class MainActivity extends AppCompatActivity {    final String zhong="zhong";    private TextView tv1,tv2;    private EditText et1;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        tv1 = (TextView) findViewById(R.id.textView);        tv2 = (TextView) findViewById(R.id.textView2);        et1 = (EditText) findViewById(R.id.edittext);        tv1.setOnClickListener(new View.OnClickListener() {            @Override            public void onClick(View view) {                write(et1.getText().toString());            }        });        tv2.setOnClickListener(new View.OnClickListener() {            @Override            public void onClick(View view) {                read();            }        });    }    private void write(String string){        try{            FileOutputStream fos = openFileOutput(zhong,MODE_APPEND);            PrintStream ps = new PrintStream(fos);            ps.println(string);            ps.close();        }catch (Exception e){            e.printStackTrace();        }    }    private String read(){        try{            FileInputStream fis = openFileInput(zhong);            byte[] buff = new byte[1024];            int hasRead = 0;            StringBuffer sb = new StringBuffer("");            while ((hasRead = fis.read(buff)) > 0){                sb.append(new String(buff,0,hasRead));            }            fis.close();            tv2.setText(sb.toString());            return sb.toString();        }catch (Exception e){            e.printStackTrace();        }        return null;    }}

布局文件：

<?xml version="1.0" encoding="utf-8"?><RelativeLayout    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"    tools:context="com.example.yh.myapplication.MainActivity">    <EditText        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:text="将要写入文件的数据"        android:id="@+id/edittext"        android:layout_centerHorizontal="true"        android:layout_marginTop="44dp" />    <TextView        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:text="存入文件"        android:id="@+id/textView"        android:layout_marginTop="137dp"        android:layout_below="@+id/edittext"        android:layout_centerHorizontal="true" />    <TextView        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:text="文件中读取的数据展示"        android:id="@+id/textView2"        android:layout_alignParentBottom="true"        android:layout_centerHorizontal="true"        android:layout_marginBottom="124dp" /></RelativeLayout>

另外记得在清单文件AndroidManifest.xml中加入读写权限：

<uses-permission android:name="android.permission.WRITE_SETTINGS" /><uses-permission android:name="com.android.launcher.permission.READ_SETTINGS" />