Android拨打接听电话自动免提

权限：

  <uses-permission android:name="android.permission.READ_PHONE_STATE"/>  
    <uses-permission android:name="android.permission.MODIFY_PHONE_STATE" />  
    <uses-permission android:name="android.permission.CALL_PHONE" />  
    <uses-permission android:name="android.permission.MODIFY_AUDIO_SETTINGS" />  

public class MainActivity extends AppCompatActivity {

    AudioManager audioManager;
    int currVolume;//当前音量

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        TelephonyManager telManager = (TelephonyManager) getSystemService(Context.TELEPHONY_SERVICE);
        TelListner listener = new TelListner();
        telManager.listen(listener, PhoneStateListener.LISTEN_CALL_STATE);
        audioManager = (AudioManager) getSystemService(Context.AUDIO_SERVICE);
    }

    public void click(View v) {
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
            if (MainActivity.this.checkSelfPermission(Manifest.permission.CALL_PHONE) == PackageManager.PERMISSION_GRANTED) {
                callPhone();
            } else {
                //
                Toast.makeText(this, "没有权限", Toast.LENGTH_LONG).show();
            }
        } else {
            callPhone();
        }
    }

    void callPhone() {
        Intent callIntent = new Intent(Intent.ACTION_CALL);
        callIntent.setData(Uri.parse("tel:10086"));
        callIntent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
        startActivity(callIntent);
    }

    private class TelListner extends PhoneStateListener {
        boolean comingPhone = false;//标识

        @Override
        public void onCallStateChanged(int state, String incomingNumber) {
            switch (state) {
                case TelephonyManager.CALL_STATE_IDLE:/* 无任何状态 */
                    if (this.comingPhone) {
                        this.comingPhone = false;
                        setSpeekModle(false);
                    }
                    break;
                case TelephonyManager.CALL_STATE_OFFHOOK:/* 接起电话 */
                    this.comingPhone = true;
                    setSpeekModle(true);
                    break;
                case TelephonyManager.CALL_STATE_RINGING:/* 电话进来 */
                    this.comingPhone = true;
                    setSpeekModle(true);
                    break;
            }
        }
    }

    void setSpeekModle(boolean open) {
        audioManager.setMode(AudioManager.ROUTE_SPEAKER);
        currVolume = audioManager.getStreamVolume(AudioManager.STREAM_VOICE_CALL);
        //5.0以上
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
            audioManager.setMode(AudioManager.MODE_IN_COMMUNICATION);

        } else {
            audioManager.setMode(AudioManager.MODE_IN_CALL);
        }

        if (!audioManager.isSpeakerphoneOn() && open) {
            Toast.makeText(MainActivity.this, "免提模式", Toast.LENGTH_LONG).show();
            audioManager.setSpeakerphoneOn(true);//开启免提
            audioManager.setStreamVolume(AudioManager.STREAM_VOICE_CALL,
                    audioManager.getStreamMaxVolume(AudioManager.STREAM_VOICE_CALL),
                    AudioManager.STREAM_VOICE_CALL);
        } else if (audioManager.isSpeakerphoneOn() && open) {
            audioManager.setSpeakerphoneOn(false);
            audioManager.setStreamVolume(AudioManager.STREAM_VOICE_CALL, currVolume,
                    AudioManager.STREAM_VOICE_CALL);
        }
    }
}

ps：此方式在华为手机上不兼容