Question

我是Android的新手，我被卡住了。我的基本前提是，当一个应用程序打开时，我需要提示用户打开蓝牙。按下是，我需要自动开始扫描附近的设备。另一个前提是我不应该使用任何按钮来开始扫描。它应该在蓝牙开启时自动启动。

代码没有语法错误。我在逻辑上做错了吗？

因为当我运行应用程序时，没有任何反应。它确实提示建立蓝牙连接，但在打开后，它应该自动扫描并填充activity_main文件中的listView。这没有发生。

activity_main.xml：

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout 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:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context="com.example.shashineha.mybluetoothapp.MainActivity">

     <ListView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id = "@+id/listView_Bluetooth"/>

</RelativeLayout>

mainActivity.java：

package com.example.bluetooth.bluetoothApp
import android.support.v7.app.AppCompatActivity;
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.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import com.example.shashineha.mybluetoothapp.R;
public class MainActivity extends AppCompatActivity {
ListView listView;
BluetoothAdapter bluetoothAdapter;
ArrayAdapter mArrayAdapter;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    bluetoothAdapter = BluetoothAdapter.getDefaultAdapter();
    if (bluetoothAdapter != null) {
        if (!bluetoothAdapter.isEnabled()) {
            Intent intent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
            startActivityForResult(intent, 0);
        }
    }
    // Register the BroadcastReceiver
    IntentFilter filter = new IntentFilter(BluetoothDevice.ACTION_FOUND);
    registerReceiver(mReceiver, filter);
}

@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    super.onActivityResult(requestCode, resultCode, data);
    if(bluetoothAdapter.isEnabled())
    {
        bluetoothAdapter.startDiscovery();
    }
}

// Create a BroadcastReceiver for ACTION_FOUND
final BroadcastReceiver mReceiver = new BroadcastReceiver() {
    public void onReceive(Context context, Intent intent) {
        listView = (ListView)findViewById(R.id.listView_Bluetooth);  
        String action = intent.getAction();
        // When discovery finds a device
        if (BluetoothDevice.ACTION_FOUND.equals(action)) {
            // Get the BluetoothDevice object from the Intent
            BluetoothDevice device = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);
            // Add the name and address to an array adapter to show in a ListView
            mArrayAdapter.add(device.getName() + "\n" + device.getAddress());
            listView.setAdapter(mArrayAdapter);
        }
    }
};


@Override
protected void onDestroy()
{
    super.onDestroy();
    unregisterReceiver(mReceiver);
    bluetoothAdapter.cancelDiscovery();
    bluetoothAdapter.disable();
}

}

androidManifest.xml：

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.bluetooth.mybluetoothapp">
<uses-permission android:name="android.permission.BLUETOOTH" />
<uses-permission android:name="android.permission.BLUETOOTH_ADMIN" />
<application
    android:allowBackup="true"
    android:icon="@mipmap/ic_launcher"
    android:label="@string/app_name"
    android:supportsRtl="true"
    android:theme="@style/AppTheme">
    <activity android:name=".MainActivity">
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />
            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>
</application>
</manifest>

Answer 1

请确保您已在清单中添加了这些权限。

Sub test()

Dim rngsize As Range, rngsize2 As Range, rngmake As Range, rngmake2 As Range, rngprice As Range, rngprice2 as range, i As Integer, j As Integer, x As Integer
x = 3
For i = 2 To Sheets("Sheet3").Range("E" & Rows.Count).End(xlUp).Row
    For j = 7 To Sheets("Sheet2").Range("E" & Rows.Count).End(xlUp).Row

        Set rngsize = Sheets("Sheet3").Range("E" & i)
        Set rngsize2 = Sheets("Sheet2").Range("E" & j)

        Set rngmake = Sheets("Sheet3").Range("F" & i)
        Set rngmake2 = Sheets("Sheet2").Range("F" & j)

        Set rngprice = Sheets("Sheet3").Range("X" & i)
        Set rngprice2 = Sheets("Sheet2").Range("X" & j)


        If rngsize * 0.5 <= rngsize And rngsize2 + 1.5 >= rngsize Then

            If rngmake2 * 0.5 <= rngmake And rngmake2 * 1.5 >= rngmake Then

                Range(Cells(Selection.Row, 1), Cells(Selection.Row, 3)).Copy

                rngprice2.Copy

                Worksheets("Sheet4").Range("F" & x).PasteSpecial Paste:=xlPasteValues

                Application.CutCopyMode = xlCopy


                x = x + 1

            End If
        End If

    Next j

Next i

End Sub

在此之后，在<uses-permission android:name="android.permission.BLUETOOTH"/> <uses-permission android:name="android.permission.BLUETOOTH_ADMIN"/>

中以这种方式改变条件

onCreate()

如果蓝牙已经打开，它将很容易开始扫描，此刻不会发生。现在它应该扫描。还要注意这一行

if (!bluetoothAdapter.isEnabled()) { Intent intent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE); startActivityForResult(intent, 0); } else { bluetoothAdapter.startDiscovery(); }

某些设备创建后，

将创建空点异常。您最初可以先查看日志消息。绑定适配器，因为它在启动时为null。还要确保你有一些可以扫描的蓝牙设备。

查询蓝牙设备android

1 个答案: