问应用程序崩溃：从Google稍微更新了蓝牙示例代码文件？

EN

AndroidManifest.xml file:
<?xml version="1.0" encoding="UTF-8"?>
<!--
 Copyright 2014 The Android Open Source Project

 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
 You may obtain a copy of the License at

     http://www.apache.org/licenses/LICENSE-2.0

 Unless required by applicable law or agreed to in writing, software
 distributed under the License is distributed on an "AS IS" BASIS,
 WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 See the License for the specific language governing permissions and
 limitations under the License.
-->

<manifest
    package="com.example.android.bluetoothchat"
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:versionCode="1"
    android:versionName="1.0">

    <!-- Min/target SDK versions (<uses-sdk>) managed by build.gradle -->

    <uses-permission android:name="android.permission.BLUETOOTH_ADMIN"/>
    <uses-permission android:name="android.permission.BLUETOOTH"/>

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme">

        <activity
            android:name=".MainActivity"
            android:configChanges="orientation|keyboardHidden"
            android:label="@string/app_name">
            <intent-filter>
                <action android:name="android.intent.action.MAIN"/>
                <category android:name="android.intent.category.LAUNCHER"/>
            </intent-filter>
        </activity>

        <activity
            android:name=".DeviceListActivity"
            android:configChanges="orientation|keyboardHidden"
            android:label="@string/select_device"
            android:theme="@android:style/Theme.Holo.Dialog"/>

    </application>
</manifest>

MainActivity.java file:

/*
* Copyright 2013 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
*     http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/


package com.example.android.bluetoothchat;

import android.os.Bundle;
import android.support.v4.app.FragmentTransaction;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.ViewAnimator;

import com.example.android.common.activities.SampleActivityBase;
import com.example.android.common.logger.Log;
import com.example.android.common.logger.LogFragment;
import com.example.android.common.logger.LogWrapper;
import com.example.android.common.logger.MessageOnlyLogFilter;

/**
 * A simple launcher activity containing a summary sample description, sample log and a custom
 * {@link android.support.v4.app.Fragment} which can display a view.
 * <p>
 * For devices with displays with a width of 720dp or greater, the sample log is always visible,
 * on other devices it's visibility is controlled by an item on the Action Bar.
 */
public class MainActivity extends SampleActivityBase {

    public static final String TAG = "MainActivity";

    // Whether the Log Fragment is currently shown
    private boolean mLogShown;

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

        if (savedInstanceState == null) {
            FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
            BluetoothChatFragment fragment = new BluetoothChatFragment();
            transaction.replace(R.id.sample_content_fragment, fragment);
            transaction.commit();
        }
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }

    @Override
    public boolean onPrepareOptionsMenu(Menu menu) {
        MenuItem logToggle = menu.findItem(R.id.menu_toggle_log);
        logToggle.setVisible(findViewById(R.id.sample_output) instanceof ViewAnimator);
        logToggle.setTitle(mLogShown ? R.string.sample_hide_log : R.string.sample_show_log);

        return super.onPrepareOptionsMenu(menu);
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        switch(item.getItemId()) {
            case R.id.menu_toggle_log:
                mLogShown = !mLogShown;
                ViewAnimator output = (ViewAnimator) findViewById(R.id.sample_output);
                if (mLogShown) {
                    output.setDisplayedChild(1);
                } else {
                    output.setDisplayedChild(0);
                }
                supportInvalidateOptionsMenu();
                return true;
        }
        return super.onOptionsItemSelected(item);
    }

    /** Create a chain of targets that will receive log data */
    @Override
    public void initializeLogging() {
        // Wraps Android's native log framework.
        LogWrapper logWrapper = new LogWrapper();
        // Using Log, front-end to the logging chain, emulates android.util.log method signatures.
        Log.setLogNode(logWrapper);

        // Filter strips out everything except the message text.
        MessageOnlyLogFilter msgFilter = new MessageOnlyLogFilter();
        logWrapper.setNext(msgFilter);

        // On screen logging via a fragment with a TextView.
        LogFragment logFragment = (LogFragment) getSupportFragmentManager()
                .findFragmentById(R.id.log_fragment);
        msgFilter.setNext(logFragment.getLogView());

        Log.i(TAG, "Ready");
    }
}


activity_main.xml file:

<!--
  Copyright 2013 The Android Open Source Project

  Licensed under the Apache License, Version 2.0 (the "License");
  you may not use this file except in compliance with the License.
  You may obtain a copy of the License at

      http://www.apache.org/licenses/LICENSE-2.0

  Unless required by applicable law or agreed to in writing, software
  distributed under the License is distributed on an "AS IS" BASIS,
  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  See the License for the specific language governing permissions and
  limitations under the License.
  -->
<LinearLayout
      xmlns:android="http://schemas.android.com/apk/res/android"
      android:orientation="vertical"
      android:layout_width="match_parent"
      android:layout_height="match_parent"
      android:id="@+id/sample_main_layout">

    <ViewAnimator
          android:id="@+id/sample_output"
          android:layout_width="match_parent"
          android:layout_height="0px"
          android:layout_weight="1">

        <ScrollView
              style="@style/Widget.SampleMessageTile"
              android:layout_width="match_parent"
              android:layout_height="match_parent">

            <TextView
                  style="@style/Widget.SampleMessage"
                  android:layout_width="match_parent"
                  android:layout_height="wrap_content"
                  android:paddingLeft="@dimen/horizontal_page_margin"
                  android:paddingRight="@dimen/horizontal_page_margin"
                  android:paddingTop="@dimen/vertical_page_margin"
                  android:paddingBottom="@dimen/vertical_page_margin"
                  android:text="@string/intro_message" />
        </ScrollView>

        <fragment
              android:name="com.example.android.common.logger.LogFragment"
              android:id="@+id/log_fragment"
              android:layout_width="match_parent"
              android:layout_height="match_parent" />

    </ViewAnimator>

    <View
          android:layout_width="match_parent"
          android:layout_height="1dp"
          android:background="@android:color/darker_gray" />

    <FrameLayout
          android:id="@+id/sample_content_fragment"
          android:layout_weight="2"
          android:layout_width="match_parent"
          android:layout_height="0px" />

</LinearLayout>

build.grade file: (this is where the changes were made)


buildscript {
    repositories {
        jcenter()
        google()
    }

    dependencies {
        classpath 'com.android.tools.build:gradle:3.1.3'
    }
}

apply plugin: 'com.android.application'

repositories {
    jcenter()
    google()
}

dependencies {
    compile "com.android.support:support-v4:27.0.2"
    compile "com.android.support:gridlayout-v7:27.0.2"
    compile "com.android.support:cardview-v7:27.0.2"
    compile "com.android.support:appcompat-v7:27.0.2"
}

// The sample build uses multiple directories to
// keep boilerplate and common code separate from
// the main sample code.
List<String> dirs = [
    'main',     // main sample code; look here for the interesting stuff.
    'common',   // components that are reused by multiple samples
    'template'] // boilerplate code that is generated by the sample template process
android {
    compileSdkVersion 27

    buildToolsVersion "27.0.3"

    defaultConfig {
        minSdkVersion 14
        targetSdkVersion 27
    }

    compileOptions {
        sourceCompatibility JavaVersion.VERSION_1_7
        targetCompatibility JavaVersion.VERSION_1_7
    }

    sourceSets {
        main {
            dirs.each { dir ->
                java.srcDirs "src/${dir}/java"
                res.srcDirs "src/${dir}/res"
            }
        }
        androidTest.setRoot('tests')
        androidTest.java.srcDirs = ['tests/src']

    }

}

06-12 21:38:10.924 3128-3128/? I/zygote: Not late-enabling -Xcheck:jni (already on)
06-12 21:38:10.933 3128-3128/? W/zygote: Unexpected CPU variant for X86 using defaults: x86
06-12 21:38:11.390 3128-3128/com.example.android.bluetoothchat I/InstantRun: starting instant run server: is main process
06-12 21:38:11.708 3128-3128/com.example.android.bluetoothchat E/BluetoothAdapter: Bluetooth binder is null
06-12 21:38:11.771 3128-3128/com.example.android.bluetoothchat D/AndroidRuntime: Shutting down VM


    --------- beginning of crash
06-12 21:38:11.773 3128-3128/com.example.android.bluetoothchat E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.example.android.bluetoothchat, PID: 3128
    java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.android.bluetoothchat/com.example.android.bluetoothchat.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'boolean android.bluetooth.BluetoothAdapter.isEnabled()' on a null object reference
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2778)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2856)
        at android.app.ActivityThread.-wrap11(Unknown Source:0)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1589)
        at android.os.Handler.dispatchMessage(Handler.java:106)
        at android.os.Looper.loop(Looper.java:164)
        at android.app.ActivityThread.main(ActivityThread.java:6494)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:438)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:807)
     Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'boolean android.bluetooth.BluetoothAdapter.isEnabled()' on a null object reference
        at com.example.android.bluetoothchat.BluetoothChatFragment.onStart(BluetoothChatFragment.java:110)
        at android.support.v4.app.Fragment.performStart(Fragment.java:2287)
        at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1458)
        at android.support.v4.app.FragmentManagerImpl.moveFragmentToExpectedState(FragmentManager.java:1750)
        at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1819)
        at android.support.v4.app.FragmentManagerImpl.dispatchStateChange(FragmentManager.java:3227)
        at android.support.v4.app.FragmentManagerImpl.dispatchStart(FragmentManager.java:3186)
        at android.support.v4.app.FragmentController.dispatchStart(FragmentController.java:203)
        at android.support.v4.app.FragmentActivity.onStart(FragmentActivity.java:582)
        at com.example.android.common.activities.SampleActivityBase.onStart(SampleActivityBase.java:39)
        at android.app.Instrumentation.callActivityOnStart(Instrumentation.java:1334)
        at android.app.Activity.performStart(Activity.java:7029)
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2741)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2856) 
        at android.app.ActivityThread.-wrap11(Unknown Source:0) 
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1589) 
        at android.os.Handler.dispatchMessage(Handler.java:106) 
        at android.os.Looper.loop(Looper.java:164) 
        at android.app.ActivityThread.main(ActivityThread.java:6494) 
        at java.lang.reflect.Method.invoke(Native Method) 
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:438) 
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:807)