Android~記錄material.tabs.TabLayout一個bug

在使用TabLayout過程當中發現一個奇葩的bug，說我xml佈局文件有問題。

一、完整log

2019-12-30 16:50:41.426 9068-9068/? E/ActivityThread: Failed to find provider info for com.mirrorlink.android.provider
2019-12-30 16:50:41.586 10184-10184/? E/AndroidRuntime: FATAL EXCEPTION: main
    java.lang.RuntimeException: Unable to start activity ComponentInfo{com.ut.smartcook/com.ut.smartcook.MainActivity}:  
     android.view.InflateException: Binary XML file line  
      #24: Binary XML file line  #24: Error inflating class com.google.android.material.tabs.TabLayout
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3021)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3156)
        at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:78)
        at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:108)
        at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:68)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1864)
        at android.os.Handler.dispatchMessage(Handler.java:106)
        at android.os.Looper.loop(Looper.java:205)
        at android.app.ActivityThread.main(ActivityThread.java:6991)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:884)
     Caused by: android.view.InflateException: Binary XML file line   
     #24: Binary XML file line #24: Error inflating class com.google.android.material.tabs.TabLayout
     Caused by: android.view.InflateException: Binary XML file line   
     #24: Error inflating class com.google.android.material.tabs.TabLayout
     Caused by: java.lang.reflect.InvocationTargetException
        at java.lang.reflect.Constructor.newInstance0(Native Method)
        at java.lang.reflect.Constructor.newInstance(Constructor.java:343)
        at android.view.LayoutInflater.createView(LayoutInflater.java:647)
        at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:790)
        at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:730)
        at android.view.LayoutInflater.rInflate(LayoutInflater.java:863)
        at android.view.LayoutInflater.rInflateChildren(LayoutInflater.java:824)
        at android.view.LayoutInflater.rInflate(LayoutInflater.java:866)
        at android.view.LayoutInflater.rInflateChildren(LayoutInflater.java:824)
        at android.view.LayoutInflater.inflate(LayoutInflater.java:515)
        at android.view.LayoutInflater.inflate(LayoutInflater.java:423)
        at android.view.LayoutInflater.inflate(LayoutInflater.java:374)
        at com.android.internal.policy.PhoneWindow.setContentView(PhoneWindow.java:435)
        at android.app.Activity.setContentView(Activity.java:2777)
        at com.ut.smartcook.MainActivity.onCreate(MainActivity.java:34)
        at android.app.Activity.performCreate(Activity.java:7159)
        at android.app.Activity.performCreate(Activity.java:7150)
        at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1272)
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3001)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3156)
        at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:78)
        at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:108)
        at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:68)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1864)
        at android.os.Handler.dispatchMessage(Handler.java:106)
        at android.os.Looper.loop(Looper.java:205)
        at android.app.ActivityThread.main(ActivityThread.java:6991)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:884)
     Caused by: java.lang.NullPointerException: Attempt to invoke virtual method   
     'int android.content.res.ColorStateList.getDefaultColor()' on a null object reference
        at com.google.android.material.tabs.TabLayout.<init>(TabLayout.java:548)
        at com.google.android.material.tabs.TabLayout.<init>(TabLayout.java:461)
        at java.lang.reflect.Constructor.newInstance0(Native Method) 
        at java.lang.reflect.Constructor.newInstance(Constructor.java:343) 
        at android.view.LayoutInflater.createView(LayoutInflater.java:647) 
        at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:790) 
        at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:730) 
        at android.view.LayoutInflater.rInflate(LayoutInflater.java:863) 
        at android.view.LayoutInflater.rInflateChildren(LayoutInflater.java:824) 
        at android.view.LayoutInflater.rInflate(LayoutInflater.java:866) 
        at android.view.LayoutInflater.rInflateChildren(LayoutInflater.java:824) 
        at android.view.LayoutInflater.inflate(LayoutInflater.java:515) 
        at android.view.LayoutInflater.inflate(LayoutInflater.java:423) 
        at android.view.LayoutInflater.inflate(LayoutInflater.java:374) 
        at com.android.internal.policy.PhoneWindow.setContentView(PhoneWindow.java:435) 
        at android.app.Activity.setContentView(Activity.java:2777) 
        at com.ut.smartcook.MainActivity.onCreate(MainActivity.java:34) 
        at android.app.Activity.performCreate(Activity.java:7159) 
        at android.app.Activity.performCreate(Activity.java:7150) 
        at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1272) 
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3001) 
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3156) 
        at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:78) 
        at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:108) 
        at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:68) 
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1864) 
        at android.os.Handler.dispatchMessage(Handler.java:106) 
        at android.os.Looper.loop(Looper.java:205) 
        at android.app.ActivityThread.main(ActivityThread.java:6991) 
        at java.lang.reflect.Method.invoke(Native Method) 
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493) 
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:884)

二、關鍵log

Caused by: android.view.InflateException: Binary XML file line #24: Binary XML file line 
#24: Error inflating class com.google.android.material.tabs.TabLayout
Caused by: android.view.InflateException: Binary XML file line   
#24: Error inflating class com.google.android.material.tabs.TabLayout

Caused by: java.lang.NullPointerException: Attempt to invoke virtual method   
'int android.content.res.ColorStateList.getDefaultColor()' on a null object reference
        at com.google.android.material.tabs.TabLayout.<init>(TabLayout.java:548)

大概意思是說Tablayout初始化時，tabTextColors = createColorStateList(tabTextColors.getDefaultColor(), selected);
tabTextColors爲空。

三、解決辦法

app:tabTextColor="#81858B"
app:tabSelectedTextColor="#31353B"

將tabTextColor放在tabSelectedTextColor以前聲明便可，若是沒在配置好tabTextColor以後配置tabSelectedTextColor會報錯！