Android设置theme中的坑

配置项目主题的时候报了如下错误:

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This Activity already has an action bar supplied by the window decor. Do not request Window.FEATURE_SUPPORT_ACTION_BAR

原因一

错误写法:

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<style name="AppTheme.NoActionBar">
<item name="android:windowActionBar">false</item>
<item name="android:windowNoTitle">true</item>
<item name="android:windowDrawsSystemBarBackgrounds">true</item>
<item name="android:statusBarColor">@android:color/transparent</item>
</style>

其中AppTheme使用的主题是AppCompat的主题,由于AppCompat主题下的windowActionBar和windowNoTitle的命名方式前都没有android字样,所以报错。

正确写法:

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<style name="AppTheme.NoActionBar">
<item name="windowActionBar">false</item>
<item name="windowNoTitle">true</item>
<item name="android:windowDrawsSystemBarBackgrounds">true</item>
<item name="android:statusBarColor">@android:color/transparent</item>
</style>

原因二

如果主题设置成有Actionbar的Theme并且没有配:

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<item name="windowActionBar">false</item>
<item name="windowNoTitle">true</item>

也会出这样的错误。

看下源码:

在我们设置toolbar时候:((AppCompatActivity)getActivity()).setSupportActionBar(toolbar);点进源码可以看到源码调用逻辑是:

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public void setSupportActionBar(@Nullable Toolbar toolbar) {
getDelegate().setSupportActionBar(toolbar);
}

在往下追一步,出真相了:

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public void setSupportActionBar(Toolbar toolbar) {
if (!(mOriginalWindowCallback instanceof Activity)) {
// Only Activities support custom Action Bars
return;
}
//这里会去判有没有actionbar存在,如果有直接抛异常
final ActionBar ab = getSupportActionBar();
if (ab instanceof WindowDecorActionBar) {
throw new IllegalStateException("This Activity already has an action bar supplied " +
"by the window decor. Do not request Window.FEATURE_SUPPORT_ACTION_BAR and set " +
"windowActionBar to false in your theme to use a Toolbar instead.");
}

// If we reach here then we're setting a new action bar
// First clear out the MenuInflater to make sure that it is valid for the new Action Bar
mMenuInflater = null;

// If we have an action bar currently, destroy it
if (ab != null) {
ab.onDestroy();
}

if (toolbar != null) {
final ToolbarActionBar tbab = new ToolbarActionBar(toolbar,
((Activity) mContext).getTitle(), mAppCompatWindowCallback);
mActionBar = tbab;
mWindow.setCallback(tbab.getWrappedWindowCallback());
} else {
mActionBar = null;
// Re-set the original window callback since we may have already set a Toolbar wrapper
mWindow.setCallback(mAppCompatWindowCallback);
}

invalidateOptionsMenu();
}

主要在这里:

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//这里会去判有没有actionbar存在,如果有直接抛异常
final ActionBar ab = getSupportActionBar();
if (ab instanceof WindowDecorActionBar) {
throw new IllegalStateException("This Activity already has an action bar supplied " +
"by the window decor. Do not request Window.FEATURE_SUPPORT_ACTION_BAR and set " +
"windowActionBar to false in your theme to use a Toolbar instead.");
}

好了,结束。