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Android随记

article 2024/11/13 17:20:30

学习笔记

- - 安卓
  - 1、recycleview
  - 2、Eventbus使用机制
  - 3、检查是否有网络
  - 4、OKHttp详解
  - 5、音视频焦点切换详解

安卓

1、recycleview

((TextView) layoutManager.findViewByPosition(mCurSiteIndex).findViewById(R.id.tv_stationname)).setTextColor(Color.parseColor("#52A8FF"));

找到recycleview中的父布局,要强制转换类型才能设置具体字体颜色

2、如果在fragment中出现无法用tv_sitefirst.setText(stations.get(0).getName());赋值
stations = mCurLine.getStations();用 = 赋值，很有可能会造空指针异常，此时可以将上面代码改为
stations.clear(); stations.addAll(mCurLine.getStations());

2、Eventbus使用机制

先在xml里面定义解析出想要的value值,然后通过下面的代码发送通知

 EventBus.getDefault().post(new StationnameEvent(value));

然后定义一个StationnameEvent类

public class StationnameEvent {

    private String txt;

    public StationnameEvent(@NonNull String txt) {
        this.txt = txt;
    }

    public String getTxt() {
        return txt;
    }
}

在要获取的地方,进行注册获取

 @Subscribe(threadMode = ThreadMode.MAIN)
    public void onReceiveStationnameEvent(StationnameEvent event) {
           //TODO 里面执行具体要执行的东西,比如显示view视图啥的.
    }

特别注意,onReceiveStationnameEvent，这个名称一定要和类的名称一模一样,否则接收不到消息。

3、检查是否有网络


    public boolean isNetworkAvailable(Activity activity)
    {
        Context context = activity.getApplicationContext();
        // 获取手机所有连接管理对象（包括对wi-fi,net等连接的管理）
        ConnectivityManager connectivityManager = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
 
        if (connectivityManager == null)
        {
            return false;
        }
        else
        {
            // 获取NetworkInfo对象
            NetworkInfo[] networkInfo = connectivityManager.getAllNetworkInfo();
 
            if (networkInfo != null && networkInfo.length > 0)
            {
                for (int i = 0; i < networkInfo.length; i++)
                {
                    System.out.println(i + "===状态===" + networkInfo[i].getState());
                    System.out.println(i + "===类型===" + networkInfo[i].getTypeName());
                    // 判断当前网络状态是否为连接状态
                    if (networkInfo[i].getState() == NetworkInfo.State.CONNECTED)
                    {
                        return true;
                    }
                }
            }
        }
        return false;
    }

4、OKHttp详解

https://www.jianshu.com/p/9aa969dd1b4d

在AndroidManifest.xml中加入联网权限

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

1、拿到OkHttpClient对象

OkHttpClient okHttpClient = new OkHttpClient()

2、构造Request对象

Request request = new Request.Builder()
                .get()
                .url("https:www.baidu.com")
                .build();

这里我们采用建造者模式和链式调用指明是进行Get请求,并传入Get请求的地址

如果我们需要在get请求时传递参数,我们可以以下面的方式将参数拼接在url之后

https:www.baidu.com?username=admin&password=admin

3、将Request封装为Call

Call call = client.newCall(request);

4、根据需要调用同步或者异步请求方法

//同步调用,返回Response,会抛出IO异常
Response response = call.execute();

//异步调用,并设置回调函数
call.enqueue(new Callback() {
    @Override
    public void onFailure(Call call, IOException e) {
        Toast.makeText(OkHttpActivity.this, "get failed", Toast.LENGTH_SHORT).show();
    }

    @Override
    public void onResponse(Call call, final Response response) throws IOException {
        final String res = response.body().string();
        runOnUiThread(new Runnable() {
            @Override
            public void run() {
                contentTv.setText(res);
            }
        });
    }
});

同步调用会阻塞主线程,一般不适用
异步调用的回调函数是在子线程,我们不能在子线程更新UI,需要借助于runOnUiThread()方法或者Handler来处理

注意：：：对okHttp连接超时进行处理

            public void onFailure(Call call, IOException e) {
                Log.e(TAG, mPlayInfo.getPdfilename() + "下载进度：连接失败-" + e.getMessage());
                // 失败终端线程
                if(e instanceof SocketTimeoutException && serversLoadTimes<BaseConstant.maxLoadTimes){如果超时并未超过指定次数，则重新连接
                    Log.e(TAG, mPlayInfo.getPdfilename() + "下载进度：超时" + e.getMessage()+"尝试第 "+serversLoadTimes+" 次");
                    serversLoadTimes++;
                    okHttpClient.newCall(call.request()).enqueue(this);
                }else {
                    Log.e(TAG, mPlayInfo.getPdfilename() + "下载出错" + e.toString());
                    interrupt();
                }
            }

5、音视频焦点切换详解

1、在播放视频的类中，进行注册

  	private AudioManager mAudioManager;
    private AudioFocusRequest audioFocusRequest;
    private AudioManager.OnAudioFocusChangeListener mAudioFocusChangeListener;

2、在oncreate进行初始化

 // 处理音频焦点-处理多个程序会来竞争音频输出设备
        mAudioManager = (AudioManager) getActivity().getSystemService(Context.AUDIO_SERVICE);

        mAudioFocusChangeListener = new AudioManager.OnAudioFocusChangeListener() {
            @Override
            public void onAudioFocusChange(int focusChange) {
                Log.e("Playfragment ", "音频焦点切换:" + focusChange);
               /* if (videoView.getBackground()==null){
                    Log.e("视频不在播放", "音频焦点切换:" + focusChange);
                    return;
                }*/
                switch (focusChange) {
                    case AudioManager.AUDIOFOCUS_GAIN:
                        // 获取audio focus
                        Log.e("Playfragment ", "获得音频焦点，提高音量" );
                        setVolume(1, videoView);
                        break;
                    case AudioManager.AUDIOFOCUS_LOSS:
                        // 失去audio focus很长一段时间，必须停止所有的audio播放，清理资源
                        Log.e("Playfragment ", "onAudioFocusChange长时间失去音频焦点，降低音量，释放资源");
                        setVolume(0, videoView);
                        break;
                    /*case AudioManager.AUDIOFOCUS_LOSS_TRANSIENT:
                        // 暂时失去audio focus，但是很快就会重新获得，在此状态应该暂停所有音频播放，但是不能清除资源
                        if (mediaPlayer.isPlaying())
                            mediaPlayer.pause();
                        break;*/
                    case AudioManager.AUDIOFOCUS_LOSS_TRANSIENT_CAN_DUCK:
                        Log.e("Playfragment ", "onAudioFocusChange短暂失去音频焦点，降低音量");
                        // 暂时失去 audio focus，但是允许持续播放音频(以很小的声音)，不需要完全停止播放。
                        setVolume(0, videoView);
                        break;
                    default:
                        break;
                }
            }
        };

3、调节音量策略

 /**
     * @param volume 音量大小
     * @param object VideoView实例
     *               ///VideoView 反射 MediaPlayer控制音量 http://blog.csdn.net/u012874222/article/details/73303264
     *               静音有效果,恢复无效
     */
    private void setVolume(float volume, Object object) {
        try {
            Log.e("Playfragment ", "播放节目，音频焦点切换设置音量:" + volume);
            Class<?> forName = Class.forName("android.widget.VideoView");
            Field field = forName.getDeclaredField("mMediaPlayer");
            field.setAccessible(true);
            MediaPlayer mMediaPlayer = (MediaPlayer) field.get(object);
            mMediaPlayer.setVolume(volume, volume);
        } catch (Exception e) {
            Log.e("Playfragment ", "播放节目，音频焦点切换设置音量" + volume + "出错:" + e.toString());
        }
    }

4、在onprepare中进行request请求

mAudioManager.requestAudioFocus(mAudioFocusChangeListener,AudioManager.STREAM_MUSIC,AudioManager.AUDIOFOCUS_GAIN);

5、进行释放资源，ondestroy

 mAudioManager.abandonAudioFocus(mAudioFocusChangeListener);

二、在需要短暂播放声音的地方（如到站播报）
1、在oncreate中

 // 处理音频焦点-处理多个程序会来竞争音频输出设备
        mAudioManager = (AudioManager) getSystemService(Context.AUDIO_SERVICE);
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
            // 对于Android 8.0+
            audioFocusRequest = new AudioFocusRequest.Builder(AudioManager.AUDIOFOCUS_GAIN_TRANSIENT)
                    .setOnAudioFocusChangeListener(mAudioFocusChangeListener).build();
            audioFocusRequest.acceptsDelayedFocusGain();
        }

2、在具体播放声音的逻辑中

 if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
                                        mAudioManager.requestAudioFocus(audioFocusRequest);
                                        Log.e(TAG, "到站播报请求音频焦点");
                                    } else {
                                        // 小于Android 8.0
                                        int result = mAudioManager.requestAudioFocus(mAudioFocusChangeListener, AudioManager.STREAM_MUSIC, AudioManager.AUDIOFOCUS_GAIN);
                                        if (result != AudioManager.AUDIOFOCUS_REQUEST_GRANTED) {
                                            // could not get audio focus.
                                            Log.e(TAG, "到站播报请求音频焦点出错:"+result);
                                        }else {
                                            Log.d(TAG, "到站播报请求音频焦点<8,"+result);
                                        }
                                    }

      mHandler.postDelayed(new Runnable() {
                                        @Override
                                        public void run() {
                                            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
                                                mAudioManager.abandonAudioFocusRequest(audioFocusRequest);
                                                Log.e(TAG, "到站播报释放音频焦点");
                                            }else {
                                                mAudioManager.abandonAudioFocus(mAudioFocusChangeListener);
                                                Log.e(TAG, "到站播报释放音频焦点<8");
                                            }
                                            mIsPlaying = false;
                                            mHandler.removeCallbacks(this);
                                        }
                                    }, 3000);
                                    break;