Android之Adapter使用方法总结

1.概念

Adapter是连接后端数据和前端显示的适配器接口(类似于csharp中的控件，绑定后端数据前端显示)，是数据和UI（View）之间一个重要的链接纽带。在常见的View(ListView,GridView)等地方都需要用到Adapter。如下图直观的表达了Data、Adapter、View三者的关系：

Android中所有的Adapter一览：

由图可以看到在Android中与Adapter有关的所有接口、类的完整层级图。在我们使用过程中可以根据自己的需求实现接口或者继承类进行一定的扩展。比较常用的有 BaseAdapter，SimpleAdapter，ArrayAdapter，SimpleCursorAdapter等。

1，BaseAdapter是一个抽象类，继承它需要实现较多的方法，所以也就具有较高的灵活性；
2，ArrayAdapter支持泛型操作，最为简单，只能展示一行字。
3，SimpleAdapter有最好的扩充性，可以自定义出各种效果。
4，SimpleCursorAdapter可以适用于简单的纯文字型ListView，它需要Cursor的字段和UI的id对应起来。如需要实现更复杂的UI也可以重写其他方法。可以认为是SimpleAdapter对数据库的简单结合，可以方便地把数据库的内容以列表的形式展示出来。

2.应用举例
首先拿七牛的PLDroidPlayerdemo来举例说明ArrayAdapter

package com.pili.pldroid.playerdemo;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.ArrayAdapter;
import android.widget.EditText;
import android.widget.RadioGroup;
import android.widget.Spinner;
import android.widget.TextView;

import com.pili.pldroid.player.PLNetworkManager;

import java.net.UnknownHostException;

public class MainActivity extends AppCompatActivity {

    private static final String DEFAULT_TEST_URL = "rtmp://live.hkstv.hk.lxdns.com/live/hks";

    private static final String[] DEFAULT_PLAYBACK_DOMAIN_ARRAY = {
            "live.hkstv.hk.lxdns.com"
    };

    private Spinner mActivitySpinner;
    private EditText mEditText;
    private RadioGroup mStreamingTypeRadioGroup;
    private RadioGroup mDecodeTypeRadioGroup;

    public static final String[] TEST_ACTIVITY_ARRAY = {
            "PLMediaPlayerActivity",
            "PLAudioPlayerActivity",
            "PLVideoViewActivity",
            "PLVideoTextureActivity",
            "VideoViewActivity"
    };

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

        try {
            PLNetworkManager.getInstance().startDnsCacheService(this, DEFAULT_PLAYBACK_DOMAIN_ARRAY);
        } catch (UnknownHostException e) {
            e.printStackTrace();
        }

        mEditText = (EditText)findViewById(R.id.VideoPathEdit);
        mEditText.setText(DEFAULT_TEST_URL);

        mStreamingTypeRadioGroup = (RadioGroup) findViewById(R.id.StreamingTypeRadioGroup);
        mDecodeTypeRadioGroup = (RadioGroup) findViewById(R.id.DecodeTypeRadioGroup);

        mActivitySpinner = (Spinner) findViewById(R.id.TestSpinner);
        ArrayAdapter adapter = new ArrayAdapter(this, android.R.layout.simple_list_item_1, TEST_ACTIVITY_ARRAY);
        mActivitySpinner.setAdapter(adapter);
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        PLNetworkManager.getInstance().stopDnsCacheService(this);
    }

    public void onClickLocalFile(View v) {
        Intent intent = new Intent(this, VideoFileActivity.class);
        startActivityForResult(intent, 0);
    }

    public void onClickPlay(View v) {
        String videopath = mEditText.getText().toString();
        if (!"".equals(videopath)) {
            jumpToPlayerActivity(videopath);
        }
    }

    public void jumpToPlayerActivity(String videopath) {
        Class cls = null;
        switch (mActivitySpinner.getSelectedItemPosition()) {
            case 0: cls = PLMediaPlayerActivity.class;
                break;
            case 1: cls = PLAudioPlayerActivity.class;
                break;
            case 2: cls = PLVideoViewActivity.class;
                break;
            case 3: cls = PLVideoTextureActivity.class;
                break;
            case 4: cls = VideoViewActivity.class;
                break;
            default:
                return;
        }
        Intent intent = new Intent(this, cls);
        intent.putExtra("videoPath", videopath);
        if (mDecodeTypeRadioGroup.getCheckedRadioButtonId() == R.id.RadioHWDecode) {
            intent.putExtra("mediaCodec", 1);
        } else {
            intent.putExtra("mediaCodec", 0);
        }
        if (mStreamingTypeRadioGroup.getCheckedRadioButtonId() == R.id.RadioLiveStreaming) {
            intent.putExtra("liveStreaming", 1);
        } else {
            intent.putExtra("liveStreaming", 0);
        }
        startActivity(intent);
    }

    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        if (resultCode != Activity.RESULT_OK) {
            return;
        }
        String videoPath = data.getStringExtra("videoPath");
        mEditText.setText(videoPath, TextView.BufferType.EDITABLE);
    }
}

上面代码简化为：

public class ArrayAdapterActivity extends ListActivity {
     @Override
     public void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         //列表项的数据
          public static final String[] TEST_ACTIVITY_ARRAY = {
            "PLMediaPlayerActivity",
            "PLAudioPlayerActivity",
            "PLVideoViewActivity",
            "PLVideoTextureActivity",
            "VideoViewActivity"
    };

        mActivitySpinner = (Spinner) findViewById(R.id.TestSpinner);
        ArrayAdapter adapter = new ArrayAdapter(this, android.R.layout.simple_list_item_1, TEST_ACTIVITY_ARRAY);
        mActivitySpinner.setAdapter(adapter);
     }
 }