Android Files的文件读取解析+代码案例

package com.example.file;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;

import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;

public class MainActivity extends AppCompatActivity {
    EditText edt;
    Button btn;
    TextView tv;

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

        edt = (EditText) findViewById(R.id.editText);
        btn = (Button) findViewById(R.id.button);
        tv = (TextView) findViewById(R.id.textView);

        btn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                WriteFiles(edt.getText().toString());
                tv.setText(readFiles());
            }
        });

    }

    //保存文件内容
    public void WriteFiles(String content){
        try {
            FileOutputStream fos = openFileOutput("a.txt",MODE_PRIVATE);
            fos.write(content.getBytes());
            fos.close();
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    //读取文件
    public String readFiles(){
        String content = null;
        try {

            FileInputStream fis =  openFileInput("a.txt");
            ByteArrayOutputStream baos = new ByteArrayOutputStream();
            byte[]buffer = new byte[1024];
            int len = 0;
            while ((len = fis.read(buffer))!=-1)
            {
                baos.write(buffer,0,len);
            }
            content = baos.toString();
            fis.close();;
            baos.close();
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
        return content;
    }
}

xml version="1.0" encoding="utf-8"?>
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:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context="com.example.file.MainActivity">

            android:layout_width="wrap_content"
        android:layout_height="200dp"
        android:id="@+id/editText"
        android:layout_alignParentTop="true"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true"
        android:layout_alignParentRight="true"
        android:layout_alignParentEnd="true" />

            android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="New Button"
        android:id="@+id/button"
        android:layout_below="@+id/editText"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="90dp" />

            android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="New Text"
        android:id="@+id/textView"
        android:layout_below="@+id/button"
        android:layout_alignParentRight="true"
        android:layout_alignParentEnd="true"
        android:layout_alignParentBottom="true"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true" />