Question

我是Android和Android的新手。正在试用Google的蓝牙API。每当我在手机上运行我的应用程序时，它会因某些原因而崩溃。我正在关注Google开发人员的API和API教程。我的MainActivity.java＆amp;更改了content.xml相应，但没有用。请看看。

这是我的 MainActivity.java

import android.content.Intent;
import android.content.Context;
import android.os.Bundle;
import android.support.design.widget.FloatingActionButton;
import android.support.design.widget.Snackbar;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.view.View;
import android.view.Menu;
import android.view.MenuItem;
import android.bluetooth.*;
import android.widget.Button;
import android.widget.Toast;


public class MainActivity extends AppCompatActivity {

    private Button btn;

    private BluetoothAdapter BA = BluetoothAdapter.getDefaultAdapter();
    private int REQUEST_ENABLE_BT = 1;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);

       /* FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
        fab.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
                        .setAction("Action", null).show();
            }
        });*/
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }

        return super.onOptionsItemSelected(item);
    }

    public void bluetoothDiscovery()
    {
     if(BA == null)
     {
         System.out.println("System Doesn't Support Bluetooth");
     }

     if(!BA.isEnabled())
     {
         Intent enableBTIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
         startActivityForResult(enableBTIntent,REQUEST_ENABLE_BT);
         Toast.makeText(MainActivity.this,"Turned On!!", Toast.LENGTH_LONG).show();
     }
     else
     {
         Toast.makeText(MainActivity.this, "ALREADY ON", Toast.LENGTH_LONG).show();
     }


    }

}

这是 AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="vertex2016.mvjce.edu.bluetoothapptry">
    <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"
            android:label="@string/app_name"
            android:theme="@style/AppTheme.NoActionBar">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

这是我的 activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<android.support.design.widget.CoordinatorLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:fitsSystemWindows="true"
    tools:context="vertex2016.mvjce.edu.bluetoothapptry.MainActivity">

    <android.support.design.widget.AppBarLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:theme="@style/AppTheme.AppBarOverlay">

        <android.support.v7.widget.Toolbar
            android:id="@+id/toolbar"
            android:layout_width="match_parent"
            android:layout_height="?attr/actionBarSize"
            android:background="?attr/colorPrimary"
            app:popupTheme="@style/AppTheme.PopupOverlay" />

    </android.support.design.widget.AppBarLayout>

    <include layout="@layout/content_main" />

  <!--  <android.support.design.widget.FloatingActionButton
        android:id="@+id/fab"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="bottom|end"
        android:layout_margin="@dimen/fab_margin"
        android:src="@android:drawable/ic_dialog_email"
        android:onClick="bluetoothDiscovery"/> -->

</android.support.design.widget.CoordinatorLayout>

这是 content.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    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"
    app:layout_behavior="@string/appbar_scrolling_view_behavior"
    tools:context="vertex2016.mvjce.edu.bluetoothapptry.MainActivity"
    tools:showIn="@layout/activity_main">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Hello World!" />

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="BTButton"
        android:id="@+id/button"
        android:layout_centerVertical="true"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true"
        android:onClick="bluetoothDiscovery"/>
</RelativeLayout>

这是我的 logcat

03-13 02:06:34.719 18759-18759/vertex2016.mvjce.edu.bluetoothapptry E/AndroidRuntime: FATAL EXCEPTION: main
                                                                                      Process: vertex2016.mvjce.edu.bluetoothapptry, PID: 18759
                                                                                      java.lang.IllegalStateException: Could not find method bluetoothDiscovery(View) in a parent or ancestor Context for android:onClick attribute defined on view class android.support.v7.widget.AppCompatButton with id 'button'
                                                                                          at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.resolveMethod(AppCompatViewInflater.java:307)
                                                                                          at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:266)
                                                                                          at android.view.View.performClick(View.java:4789)
                                                                                          at android.view.View$PerformClick.run(View.java:19881)
                                                                                          at android.os.Handler.handleCallback(Handler.java:739)
                                                                                          at android.os.Handler.dispatchMessage(Handler.java:95)
                                                                                          at android.os.Looper.loop(Looper.java:135)
                                                                                          at android.app.ActivityThread.main(ActivityThread.java:5292)
                                                                                          at java.lang.reflect.Method.invoke(Native Method)
                                                                                          at java.lang.reflect.Method.invoke(Method.java:372)
                                                                                          at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:904)
                                                                                          at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:699)

感谢您的时间

Answer 1

您的方法bluetoothDiscovery必须接受View类型的参数，请参阅View.onClick以供参考。

public void bluetoothDiscovery(View v) {}

调用此方法时，v将是单击的View对象。

即

switch ( v.getId() ) {
    case R.id.button:
        // do something
        break;
    case R.id.other_button
        // do something else
        break;
}

r.id.button 来自您在XML中的定义，

android:id="@+id/button"

正是使用它，你可以有一个由多个按钮调用的onClick方法，每个按钮都有自己的动作。

Answer 2

您需要在onClick方法中使用View参数

public void bluetoothDiscovery(View v)

就个人而言，我尽量不在XML中添加onClick，因为在添加更多类和布局时很难找到它们。您可以从Java代码中设置OnClickListener以获得更清晰的可见性。

按下按钮时蓝牙应用程序崩溃

2 个答案: