Android测试读写sd卡文件与写sd卡文件耗时

　　测试从sd卡读1k大小的文件，再写1k大小的文件，由于处理耗时很短，所以循环500次，查看耗时；测试写1k大小的文件，直接在内存构造一个1k的buffer，将这个buffer直接写到文件，同样循环500次，查看耗时。

　　思路：首先读写文件，建立文件输入输出流，然后将读取的数据直接写入文件，打印时间戳，查看耗时；只写文件，新建一个1k的buffer，然后用文件输出流写入文件，打印时间戳，查看耗时。

　　直接上代码：

　　

  1 package com.example.ghimtim.myapplication;
  2 
  3 import android.Manifest;
  4 import android.content.Context;
  5 import android.content.pm.PackageManager;
  6 import android.os.Environment;
  7 import android.os.SystemClock;
  8 import android.support.v4.app.ActivityCompat;
  9 import android.support.v4.content.ContextCompat;
 10 import android.support.v7.app.AppCompatActivity;
 11 import android.os.Bundle;
 12 import android.view.View;
 13 import android.widget.Button;
 14 import android.widget.EditText;
 15 import android.widget.TextView;
 16 import android.widget.Toast;
 17 
 18 import java.io.File;
 19 import java.io.FileInputStream;
 20 import java.io.FileOutputStream;
 21 import java.io.InputStreamReader;
 22 import java.io.OutputStreamWriter;
 23 
 24 public class MainActivity extends AppCompatActivity implements ActivityCompat.OnRequestPermissionsResultCallback{
 25 
 26     private static final int MY_PERMISSIONS_REQUEST = 10000;
 27 
 28     private Button bt_wr;
 29     private Button bt_w;
 30     private TextView tv_wr;
 31     private TextView tv_w;
 32     private EditText et_time;
 33     private File sdcard;
 34 
 35     private Context mContext;
 36 
 37     int Fortime = 1000;
 38     char[] buffer = new char[1024];
 39     long time;
 40 
 41 
 42     @Override
 43     protected void onCreate(Bundle savedInstanceState) {
 44         super.onCreate(savedInstanceState);
 45         setContentView(R.layout.activity_main);
 46         mContext = this;
 47         requestpermisson();
 48         sdcard= Environment.getExternalStorageDirectory();
 49         initData();
 50         initView();
 51     }
 52 
 53     private void initData() {
 54         for(int i = 0 ; i < 1024;i++){
 55             buffer[i] = 'b';
 56         }
 57     }
 58 
 59     private void requestpermisson() {
 60         ActivityCompat.requestPermissions(this,
 61             new String[]{Manifest.permission.WRITE_EXTERNAL_STORAGE},
 62                 MY_PERMISSIONS_REQUEST);
 63 
 64     }
 65 
 66     @Override
 67     public void onRequestPermissionsResult(int requestCode,
 68                                            String permissions[], int[] grantResults) {
 69         switch (requestCode) {
 70             case MY_PERMISSIONS_REQUEST: {
 71                 // If request is cancelled, the result arrays are empty.
 72                 if (grantResults.length > 0
 73                         && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
 74 
 75                     // permission was granted, yay! Do the
 76                     // contacts-related task you need to do.
 77 
 78                 } else {
 79                   Toast.makeText(this,"no permission!",Toast.LENGTH_LONG).show();
 80 //                    this.finish();
 81                     // permission denied, boo! Disable the
 82                     // functionality that depends on this permission.
 83                 }
 84                 return;
 85             }
 86         }
 87     }
 88 
 89     private void initView() {
 90         bt_wr = (Button) findViewById(R.id.write_read_sd_file);
 91         bt_w = (Button) findViewById(R.id.write_sd_file);
 92         tv_wr = (TextView) findViewById(R.id.write_read_sd_file_time);
 93         tv_w = (TextView) findViewById(R.id.write_sd_file_time);
 94         et_time = (EditText) findViewById(R.id.for_time);
 95         et_time.setText(String.valueOf(Fortime));
 96         bt_wr.setOnClickListener(new View.OnClickListener() {
 97             @Override
 98             public void onClick(View v) {
 99                 if(!et_time.getText().toString().equals("")){
100                     Fortime =  Integer.parseInt(et_time.getText().toString());
101                 }
102                 time = System.currentTimeMillis();
103                 writeAndReadForTime();
104 
105             }
106         });
107         bt_w.setOnClickListener(new View.OnClickListener() {
108             @Override
109             public void onClick(View v) {
110                 if(!et_time.getText().toString().equals("")){
111                     Fortime =  Integer.parseInt(et_time.getText().toString());
112                 }
113                 time = System.currentTimeMillis();
114                 ReadFileForTime();
115             }
116         });
117     }
118 
119     private void ReadFileForTime() {
120         for(int i =0;i){
121             ReadFile();
122         }
123         time = System.currentTimeMillis() - time;
124         tv_w.setText(String.valueOf(time));
125     }
126 
127     private void writeAndReadForTime() {
128         for(int i =0;i){
129             writeAndRead();
130         }
131         time = System.currentTimeMillis() - time;
132         tv_wr.setText(String.valueOf(time));
133     }
134 
135     private void ReadFile() {
136         File file2 =  new File(sdcard,"c.txt");
137         if(!sdcard.exists()){
138             return;
139         }
140         try{
141 //            file2.createNewFile();
142             FileOutputStream fos=new FileOutputStream(file2);
143             OutputStreamWriter osw=new OutputStreamWriter(fos);
144             String str = new String(buffer);
145             osw.write(str);
146             osw.flush();
147             osw.close();
148             fos.close();
149         }catch (Exception e){
150             e.printStackTrace();
151         }
152     }
153 
154     private void writeAndRead() {
155         File file1 = new File(sdcard,"a.txt");
156         File file2 =  new File(sdcard,"b.txt");
157         if(!sdcard.exists()){
158             return;
159         }
160         try{
161 //            file2.createNewFile();
162             FileInputStream fis = new FileInputStream(file1);
163             InputStreamReader isr = new InputStreamReader(fis,"UTF-8");
164             FileOutputStream fos=new FileOutputStream(file2);
165             OutputStreamWriter osw=new OutputStreamWriter(fos);
166             char[] input =  new char[fis.available()];
167             isr.read(input);
168             String str = new String(input);
169             osw.write(str);
170             osw.flush();
171             isr.close();
172             fis.close();
173             osw.close();
174             fos.close();
175         }catch (Exception e){
176             e.printStackTrace();
177         }
178     }
179 }

　　还有一个注意的地方，读写sd卡，在Android6.0以后需要动态申请读写外部存储的权限！

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

　　（编码时粗心地将uses-permission写进application标签里面= =，这个uses-permission是应该要和application同级的。。。）

　　

转载于:https://www.cnblogs.com/ghimtim/p/7045953.html