Android Assets（资产）

Android还提供了一个目录来存储资源文件：/assets 。

/assets 与 /res 的级别相同。

/assets 中的文件不会在 R.java 中生成ID。你必须指定读取它们的文件路径。

文件路径是以/assets 开头的相对路径。

例子

你可以使用 AssetManager 类来访问这些文件。

String getStringFromAssetFile(Activity activity)
{
   AssetManager am = activity.getAssets();
   InputStream is = am.open("test.txt");
   String s = convertStreamToString(is);
   is.close();
   return s;
}

加载位于assets文件夹中的HTML文件

以下代码显示如何加载位于assets文件夹中的HTML文件。

主布局xml文件

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
      android:orientation="vertical" >

  <WebView android:id="@+id/webview1"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content" />

</LinearLayout>

在MainActivity.java文件中，添加以下语句:

import android.app.Activity;
import android.os.Bundle;
import android.webkit.WebSettings;
import android.webkit.WebView;
/*from www.w3cschool.cn*/
public class MainActivity extends Activity {
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        WebView wv = (WebView) findViewById(R.id.webview1);
        wv.loadUrl("file:///android_asset/Index.html");

    }
}

从asset文件夹读取并解析CSV文件

下面的代码显示了如何从asset文件夹读取并解析CSV文件。

注册 WRITE_EXTERNAL_STORAGE 的权限

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="cn.w3cschool.myapplication3.app" >
    <uses-sdk
        android:minSdkVersion="8"
        android:targetSdkVersion="18" />
    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="www.w3cschool.cn"
        android:theme="@style/AppTheme" >
        <activity
            android:name="cn.w3cschool.myapplication3.app.MainActivity"
            android:label="www.w3cschool.cn"
            >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

主Activity的Java代码

package cn.w3cschool.myapplication3.app;
//from  www.w3cschool.cn
import android.app.Activity;
import android.content.res.AssetManager;
import android.os.Bundle;
import android.util.Log;
import android.widget.TextView;

import java.io.BufferedReader;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.ArrayList;

public class MainActivity extends Activity {

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        TextView tv = new TextView(this);
        setContentView(tv);

        try {
            AssetManager manager = getAssets();
            InputStream in = manager.open("data.csv");

            ArrayList<Person> cooked = parse(in);
            StringBuilder builder = new StringBuilder();
            for(Person piece : cooked) {
                builder.append(String.format("%s is %s years old, and likes the color %s",
                        piece.name, piece.age, piece.color));
                builder.append("\n");
            }
            tv.setText(builder.toString());

        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }

    }

    /* Simple CSV Parser */
    private static final int COL_NAME = 0;
    private static final int COL_AGE = 1;
    private static final int COL_COLOR = 2;

    private ArrayList<Person> parse(InputStream in) throws IOException {
        ArrayList<Person> results = new ArrayList<Person>();

        BufferedReader reader = new BufferedReader(new InputStreamReader(in));
        String nextLine = null;
        while ((nextLine = reader.readLine()) != null) {
            String[] tokens = nextLine.split(",");
            if (tokens.length != 3) {
                Log.w("CSVParser", "Skipping Bad CSV Row");
                continue;
            }
            //Add new parsed result
            Person current = new Person();
            current.name = tokens[COL_NAME];
            current.color = tokens[COL_COLOR];
            current.age = tokens[COL_AGE];

            results.add(current);
        }
        in.close();
        return results;
    }
}
class Person {
    public String name;
    public String age;
    public String color;

    public Person() { }
}

data.csv

Jack,Red,12
Jane,Black,13
Jode,Brown,14