在Android studio中编写一个用听筒发射频率从16kHz-22kHz线性递增的长为1ms的声波，然后接收反射信号并显示频谱图的代码

以下是一个可能的实现：

import android.media.AudioFormat;
import android.media.AudioManager;
import android.media.AudioTrack;
import android.media.AudioRecord;
import android.media.MediaRecorder;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;

import androidx.appcompat.app.AppCompatActivity;

import java.util.Arrays;

public class MainActivity extends AppCompatActivity {

    private static final String TAG = "MainActivity";

    private static final int SAMPLE_RATE = 44100;
    private static final int CHANNEL_CONFIG = AudioFormat.CHANNEL_OUT_MONO;
    private static final int AUDIO_FORMAT = AudioFormat.ENCODING_PCM_16BIT;
    private static final int BUFFER_SIZE = AudioRecord.getMinBufferSize(SAMPLE_RATE, AudioFormat.CHANNEL_IN_MONO, AudioFormat.ENCODING_PCM_16BIT);

    private static final int MIN_FREQUENCY = 16000;
    private static final int MAX_FREQUENCY = 22000;
    private static final int SIGNAL_DURATION = 1000; // in ms
    private static final int SIGNAL_LENGTH = SAMPLE_RATE * SIGNAL_DURATION / 1000;
    private static final double PI_2 = Math.PI * 2;

    private AudioTrack mAudioTrack;
    private AudioRecord mAudioRecord;
    private short[] mSignalBuffer;
    private short[] mRecordBuffer;
    private double[] mFFTBuffer;
    private boolean mIsPlaying;
    private boolean mIsRecording;
    private Button mButton;
    private TextView mTextView;
    private Handler mHandler;

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

        mButton = findViewById(R.id.button);
        mTextView = findViewById(R.id.textView);

        mHandler = new Handler() {
            @Override
            public void handleMessage(Message msg) {
                if (msg.what == 1) {
                    double[] fft = (double[]) msg.obj;
                    mTextView.setText(Arrays.toString(fft));
                }
            }
        };

        mSignalBuffer = new short[SIGNAL_LENGTH];
        mRecordBuffer = new short[BUFFER_SIZE];
        mFFTBuffer = new double[BUFFER_SIZE];

        for (int i = 0; i < SIGNAL_LENGTH; i++) {
            double t = (double) i / SAMPLE_RATE;
            double f = MIN_FREQUENCY + (MAX_FREQUENCY - MIN_FREQUENCY) * t / SIGNAL_DURATION;
            mSignalBuffer[i] = (short) (Short.MAX_VALUE * Math.sin(PI_2 * f * t));
        }

        mAudioTrack = new AudioTrack(AudioManager.STREAM_VOICE_CALL, SAMPLE_RATE, CHANNEL_CONFIG, AUDIO_FORMAT, SIGNAL_LENGTH, AudioTrack.MODE_STATIC);
        mAudioTrack.write(mSignalBuffer, 0, SIGNAL_LENGTH);

        mAudioRecord = new AudioRecord(MediaRecorder.AudioSource.MIC, SAMPLE_RATE, AudioFormat.CHANNEL_IN_MONO, AudioFormat.ENCODING_PCM_16BIT, BUFFER_SIZE);

        mButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if (mIsPlaying) {
                    mAudioTrack.stop();
                    mIsPlaying = false;
                    mButton.setText("Start");
                } else {
                    mAudioTrack.play();
                    mIsPlaying = true;
                    mButton.setText("Stop");
                    new Thread(new Runnable() {
                        @Override
                        public void run() {
                            while (mIsPlaying) {
                                int n = mAudioRecord.read(mRecordBuffer, 0, BUFFER_SIZE);
                                for (int i = 0; i < n; i++) {
                                    mFFTBuffer[i] = mRecordBuffer[i];
                                }
                                FFT.fft(mFFTBuffer);
                                Message msg = mHandler.obtainMessage(1, mFFTBuffer);
                                mHandler.sendMessage(msg);
                            }
                        }
                    }).start();
                }
            }
        });
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        mAudioTrack.release();
        mAudioRecord.release();
    }
}

这个代码使用了 Android 的音频 API，通过 `AudioTrack` 发射一个从 16kHz 到 22kHz 线性递增的声波，长度为 1ms。然后通过 `AudioRecord` 接收反射信号，并使用 FFT 算法计算频谱图。最后将频谱图显示在界面上。

需要注意的是，这个代码只是一个示例，可能存在一些问题，比如声波的质量可能不够好，频谱图的计算可能不够准确等。如果需要更高质量的声波和频谱图，需要更加深入地研究音频处理和信号处理的知识。