向上导航到父 activity 时 Recycler View 崩溃
Recycler View crashes when navigating up to parent activity
我是 Android、Java 和 Kotlin 的新手,我正在尝试移植我的应用程序,该应用程序最初是为 iOS 在 Swift 中编写的。
应用程序使用的数据是我的 Speaker 对象的 ArrayList,来自 JSON 文件。
我的 MainActivity 显示一个由每个扬声器的“品牌”参数填充的 RecyclerView。每行的 onClick 都会启动带有 recyclerView 的 BrandMenuActivity 以及该品牌的所有扬声器。这些的 onClick 然后显示一个 detailView。
在模拟器中使用“硬件”后退按钮导航时一切正常,但如果我尝试在 detailView 的操作栏中实现 setDisplayHomeAsUpEnabled,应用程序会崩溃,因为 BrandMenuActivity 的意图现在为空。
我的Android清单:
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.speakerskotlin">
<application
android:allowBackup="true"
android:icon="@mipmap/ic_launcher"
android:label="@string/app_name"
android:roundIcon="@mipmap/ic_launcher_round"
android:supportsRtl="true"
android:theme="@style/AppTheme">
<activity android:name=".SpeakerDetailActivity"
android:parentActivityName=".BrandMenuActivity">
</activity>
<activity android:name=".BrandMenuActivity"
android:parentActivityName=".MainActivity" >
</activity>
<activity android:name=".MainActivity">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
主要活动:
class MainActivity : AppCompatActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
setSupportActionBar(findViewById(R.id.speakerToolbar))
supportActionBar?.title = "Speakers"
val jsonFileString = getJsonDataFromAsset(applicationContext, "SpeakerData.json")
val gson = Gson()
val listSpeakerType = object : TypeToken<ArrayList<Speaker>>() {}.type
val allSpeakers: ArrayList<Speaker> = gson.fromJson(jsonFileString, listSpeakerType)
brandsRecView.layoutManager = LinearLayoutManager(this)
brandsRecView.adapter = SpeakerBrandAdapter(allSpeakers){
val intent = Intent(this, BrandMenuActivity::class.java)
intent.putExtra("allSpeakers", allSpeakers)
intent.putExtra("brand", it)
startActivity(intent)
}
}
品牌菜单活动:
class BrandMenuActivity() : AppCompatActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_brand_menu)
setSupportActionBar(findViewById(R.id.brandToolbar))
supportActionBar?.title = intent.getStringExtra("brand")
supportActionBar?.setDisplayHomeAsUpEnabled(true)
val brand = intent.getStringExtra("brand")
val allSpeakers: ArrayList<Speaker> = intent.getParcelableArrayListExtra("allSpeakers")
brandMenuRecView.layoutManager = LinearLayoutManager(this.applicationContext)
brandMenuRecView.adapter = BrandMenuAdapter(brand, allSpeakers) {
val intent = Intent(this, SpeakerDetailActivity::class.java)
intent.putExtra("speaker", it)
startActivity(intent)
}
}
详细活动:
class SpeakerDetailActivity: AppCompatActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_speaker_detail)
setSupportActionBar(findViewById(R.id.detailToolbar))
supportActionBar?.setDisplayHomeAsUpEnabled(true)
val speaker = intent.getParcelableExtra<Speaker>("speaker")
val modelImage = findViewById<ImageView>(R.id.imgSpeakerImage)
val brandText = findViewById<TextView>(R.id.txtBrandName)
val modelText = findViewById<TextView>(R.id.txtModel)
brandText.text = speaker.brand
modelText.text = speaker.model
val resID = resources.getIdentifier(speaker.imgString, "drawable", packageName)
modelImage.setImageResource(resID)
speakerDetailRecView.layoutManager = LinearLayoutManager(this.applicationContext)
speakerDetailRecView.adapter = SpeakerDetailAdapter(speaker)
}
崩溃时的Log:
E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.speakerskotlin, PID: 12099
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.speakerskotlin/com.example.speakerskotlin.BrandMenuActivity}: java.lang.IllegalStateException: intent.getParcelableArrayListExtra("allSpeakers") must not be null
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3270)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3409)
at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:83)
at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135)
at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2016)
at android.os.Handler.dispatchMessage(Handler.java:107)
at android.os.Looper.loop(Looper.java:214)
at android.app.ActivityThread.main(ActivityThread.java:7356)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:492)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:930)
Caused by: java.lang.IllegalStateException: intent.getParcelableArrayListExtra("allSpeakers") must not be null
at com.example.speakerskotlin.BrandMenuActivity.onCreate(BrandMenuActivity.kt:20)
at android.app.Activity.performCreate(Activity.java:7802)
at android.app.Activity.performCreate(Activity.java:7791)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1299)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3245)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3409)
at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:83)
at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135)
at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2016)
at android.os.Handler.dispatchMessage(Handler.java:107)
at android.os.Looper.loop(Looper.java:214)
at android.app.ActivityThread.main(ActivityThread.java:7356)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:492)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:930)
两种方法。
第一个是,您可以尝试在点击 android.R.id.home
时调用 finish()
override fun onOptionsItemSelected(item: MenuItem): Boolean {
if (item.itemId == android.R.id.home) {
finish()
return true
}
return super.onOptionsItemSelected(item)
}
这只是恢复您的 BrandMenuActivity
,因此不会调用 onCreate,您可以查看完整的视频教程 here。
第二个是,如果您想要来自 SpeakerDetailActivity
的相同意图数据,只需像解释的那样在活动之间传递数据 here
我是 Android、Java 和 Kotlin 的新手,我正在尝试移植我的应用程序,该应用程序最初是为 iOS 在 Swift 中编写的。
应用程序使用的数据是我的 Speaker 对象的 ArrayList,来自 JSON 文件。
我的 MainActivity 显示一个由每个扬声器的“品牌”参数填充的 RecyclerView。每行的 onClick 都会启动带有 recyclerView 的 BrandMenuActivity 以及该品牌的所有扬声器。这些的 onClick 然后显示一个 detailView。
在模拟器中使用“硬件”后退按钮导航时一切正常,但如果我尝试在 detailView 的操作栏中实现 setDisplayHomeAsUpEnabled,应用程序会崩溃,因为 BrandMenuActivity 的意图现在为空。
我的Android清单:
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.speakerskotlin">
<application
android:allowBackup="true"
android:icon="@mipmap/ic_launcher"
android:label="@string/app_name"
android:roundIcon="@mipmap/ic_launcher_round"
android:supportsRtl="true"
android:theme="@style/AppTheme">
<activity android:name=".SpeakerDetailActivity"
android:parentActivityName=".BrandMenuActivity">
</activity>
<activity android:name=".BrandMenuActivity"
android:parentActivityName=".MainActivity" >
</activity>
<activity android:name=".MainActivity">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
主要活动:
class MainActivity : AppCompatActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
setSupportActionBar(findViewById(R.id.speakerToolbar))
supportActionBar?.title = "Speakers"
val jsonFileString = getJsonDataFromAsset(applicationContext, "SpeakerData.json")
val gson = Gson()
val listSpeakerType = object : TypeToken<ArrayList<Speaker>>() {}.type
val allSpeakers: ArrayList<Speaker> = gson.fromJson(jsonFileString, listSpeakerType)
brandsRecView.layoutManager = LinearLayoutManager(this)
brandsRecView.adapter = SpeakerBrandAdapter(allSpeakers){
val intent = Intent(this, BrandMenuActivity::class.java)
intent.putExtra("allSpeakers", allSpeakers)
intent.putExtra("brand", it)
startActivity(intent)
}
}
品牌菜单活动:
class BrandMenuActivity() : AppCompatActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_brand_menu)
setSupportActionBar(findViewById(R.id.brandToolbar))
supportActionBar?.title = intent.getStringExtra("brand")
supportActionBar?.setDisplayHomeAsUpEnabled(true)
val brand = intent.getStringExtra("brand")
val allSpeakers: ArrayList<Speaker> = intent.getParcelableArrayListExtra("allSpeakers")
brandMenuRecView.layoutManager = LinearLayoutManager(this.applicationContext)
brandMenuRecView.adapter = BrandMenuAdapter(brand, allSpeakers) {
val intent = Intent(this, SpeakerDetailActivity::class.java)
intent.putExtra("speaker", it)
startActivity(intent)
}
}
详细活动:
class SpeakerDetailActivity: AppCompatActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_speaker_detail)
setSupportActionBar(findViewById(R.id.detailToolbar))
supportActionBar?.setDisplayHomeAsUpEnabled(true)
val speaker = intent.getParcelableExtra<Speaker>("speaker")
val modelImage = findViewById<ImageView>(R.id.imgSpeakerImage)
val brandText = findViewById<TextView>(R.id.txtBrandName)
val modelText = findViewById<TextView>(R.id.txtModel)
brandText.text = speaker.brand
modelText.text = speaker.model
val resID = resources.getIdentifier(speaker.imgString, "drawable", packageName)
modelImage.setImageResource(resID)
speakerDetailRecView.layoutManager = LinearLayoutManager(this.applicationContext)
speakerDetailRecView.adapter = SpeakerDetailAdapter(speaker)
}
崩溃时的Log:
E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.speakerskotlin, PID: 12099
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.speakerskotlin/com.example.speakerskotlin.BrandMenuActivity}: java.lang.IllegalStateException: intent.getParcelableArrayListExtra("allSpeakers") must not be null
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3270)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3409)
at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:83)
at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135)
at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2016)
at android.os.Handler.dispatchMessage(Handler.java:107)
at android.os.Looper.loop(Looper.java:214)
at android.app.ActivityThread.main(ActivityThread.java:7356)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:492)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:930)
Caused by: java.lang.IllegalStateException: intent.getParcelableArrayListExtra("allSpeakers") must not be null
at com.example.speakerskotlin.BrandMenuActivity.onCreate(BrandMenuActivity.kt:20)
at android.app.Activity.performCreate(Activity.java:7802)
at android.app.Activity.performCreate(Activity.java:7791)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1299)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3245)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3409)
at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:83)
at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135)
at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2016)
at android.os.Handler.dispatchMessage(Handler.java:107)
at android.os.Looper.loop(Looper.java:214)
at android.app.ActivityThread.main(ActivityThread.java:7356)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:492)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:930)
两种方法。
第一个是,您可以尝试在点击 android.R.id.home
override fun onOptionsItemSelected(item: MenuItem): Boolean {
if (item.itemId == android.R.id.home) {
finish()
return true
}
return super.onOptionsItemSelected(item)
}
这只是恢复您的 BrandMenuActivity
,因此不会调用 onCreate,您可以查看完整的视频教程 here。
第二个是,如果您想要来自 SpeakerDetailActivity
的相同意图数据,只需像解释的那样在活动之间传递数据 here