BluetoothAdapter在Android6.0+以上startDiscovery不能发现蓝牙设备问题
问题的重要原因之一是Android 6.0+，Android 7.0+的权限问题引起的。在Android 4.0+上运行良好的蓝牙代码，在高版本运行异常。比如BluetoothAdapter的startDiscovery虽然启动了发现蓝牙任务，但是不能发现蓝牙设备。解决问题是针对最新高版本的Android系统增加权限申请。现在给出一个完整例子。
activity_main.xml：
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
tools:context="zhangphil.bluetooth.MainActivity">
<Button
android:id="@+id/init"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="初始化蓝牙设备" />
<Button
android:id="@+id/discovery"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="发现设备" />
<Button
android:id="@+id/enable_discovery"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="使自身可被其他蓝牙设备发现" />
<ListView
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:id="@+id/listView">
</ListView>
</LinearLayout>
测试的MainActivity.java：
package zhangphil.bluetooth;
import android.Manifest;
import android.app.Activity;
import android.bluetooth.BluetoothAdapter;
import android.bluetooth.BluetoothDevice;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.content.pm.PackageManager;
import android.os.Build;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.ArrayAdapter;
import android.widget.ListView;
public class MainActivity extends Activity implements View.OnClickListener {
private final int REQUEST_ENABLE_BT = 0xa01;
private final int PERMISSION_REQUEST_COARSE_LOCATION = 0xb01;
private String TAG = "zhangphil";
private ArrayAdapter<String> mAdapter;
private BluetoothAdapter mBluetoothAdapter;
// 广播接收发现蓝牙设备
private BroadcastReceiver mReceiver = new BroadcastReceiver() {
@Override
public void onReceive(Context context, Intent intent) {
String action = intent.getAction();
if (BluetoothAdapter.ACTION_DISCOVERY_STARTED.equals(action)) {
Log.d(TAG, "开始扫描...");
}
if (BluetoothDevice.ACTION_FOUND.equals(action)) {
BluetoothDevice device = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);
if (device != null) {
// 添加到ListView的Adapter。
mAdapter.add("设备名:" + device.getName() + "\n设备地址:" + device.getAddress());
mAdapter.notifyDataSetChanged();
}
}
if (BluetoothAdapter.ACTION_DISCOVERY_FINISHED.equals(action)) {
Log.d(TAG, "扫描结束.");
}
}
};
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
if (this.checkSelfPermission(Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
requestPermissions(new String[]{Manifest.permission.ACCESS_COARSE_LOCATION}, PERMISSION_REQUEST_COARSE_LOCATION);
}
}
// 注册广播接收器。
// 接收蓝牙发现
IntentFilter filterFound = new IntentFilter(BluetoothDevice.ACTION_FOUND);
registerReceiver(mReceiver, filterFound);
IntentFilter filterStart = new IntentFilter(BluetoothAdapter.ACTION_DISCOVERY_STARTED);
registerReceiver(mReceiver, filterStart);
IntentFilter filterFinish = new IntentFilter(BluetoothAdapter.ACTION_DISCOVERY_FINISHED);
registerReceiver(mReceiver, filterFinish);
mAdapter = new ArrayAdapter<>(this, android.R.layout.simple_list_item_1, android.R.id.text1);
((ListView) findViewById(R.id.listView)).setAdapter(mAdapter);
findViewById(R.id.init).setOnClickListener(this);
findViewById(R.id.discovery).setOnClickListener(this);
findViewById(R.id.enable_discovery).setOnClickListener(this);
}
@Override
public void onClick(View view) {
switch (view.getId()) {
case R.id.init:
init();
case R.id.discovery:
discovery();
case R.id.enable_discovery:
enable_discovery();
}
}
// 初始化蓝牙设备
private void init() {
mBluetoothAdapter = BluetoothAdapter.getDefaultAdapter();
// 检查设备是否支持蓝牙设备
if (mBluetoothAdapter == null) {
Log.d(TAG, "设备不支持蓝牙");
// 不支持蓝牙，退出。
return;
}
// 如果用户的设备没有开启蓝牙，则弹出开启蓝牙设备的对话框，让用户开启蓝牙
if (!mBluetoothAdapter.isEnabled()) {
Log.d(TAG, "请求用户打开蓝牙");
Intent enableBtIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
startActivityForResult(enableBtIntent, REQUEST_ENABLE_BT);
// 接下去，在onActivityResult回调判断
}
}
// 启动蓝牙发现...
private void discovery() {
if (mBluetoothAdapter == null) {
init();
}
mBluetoothAdapter.startDiscovery();
}
// 可选方法，非必需
// 此方法使自身的蓝牙设备可以被其他蓝牙设备扫描到，
// 注意时间阈值。0 - 3600 秒。
// 通常设置时间为120秒。
private void enable_discovery() {
Intent discoverableIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_DISCOVERABLE);
// 第二个参数可设置的范围是0~3600秒，在此时间区间（窗口期）内可被发现
// 任何不在此区间的值都将被自动设置成120秒。
discoverableIntent.putExtra(BluetoothAdapter.EXTRA_DISCOVERABLE_DURATION, 3600);
startActivity(discoverableIntent);
}
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
super.onActivityResult(requestCode, resultCode, data);
if (requestCode == REQUEST_ENABLE_BT) {
if (resultCode == RESULT_OK) {
Log.d(TAG, "打开蓝牙成功！");
}
if (resultCode == RESULT_CANCELED) {
Log.d(TAG, "放弃打开蓝牙！");
}
} else {
Log.d(TAG, "蓝牙异常！");
}
}
@Override
protected void onDestroy() {
super.onDestroy();
unregisterReceiver(mReceiver);
}
@Override
public void onRequestPermissionsResult(int requestCode, String permissions[], int[] grantResults) {
switch (requestCode) {
case PERMISSION_REQUEST_COARSE_LOCATION:
if (grantResults[0] == PackageManager.PERMISSION_GRANTED) {
}
break;
}
}
}不要忘记增加权限：
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />
<uses-permission android:name="android.permission.BLUETOOTH" />
<uses-permission android:name="android.permission.BLUETOOTH_ADMIN" />代码运行结果：
以上代码运行测试环境：硬件设备是三星S7Edge，Android版本：7.0
