Android设置theme中的坑

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配置项目主题的时候报了如下错误：

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：

<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：

<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：

<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：

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

在往下追一步，出真相了：

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：

//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。