Android-用style修改AlertDialog按鈕文字顏色

android系統爲開發者提供了AlertDialog,用於快捷創建dialog。

用Builder模式創建，可以輕鬆設置title,message,取消，確定按鈕點擊事件等。但是本人實際項目用的比較少，因爲跟UI設計的樣式不太一樣，按鈕文字顏色不太好修改。經過一番查找，找到了修改按鈕文字顏色的方法。

AlertDialog最底層的構造方法：

/**
     * Construct an AlertDialog that uses an explicit theme.  The actual style
     * that an AlertDialog uses is a private implementation, however you can
     * here supply either the name of an attribute in the theme from which
     * to get the dialog's style (such as {@link R.attr#alertDialogTheme}.
     */
    protected AlertDialog(@NonNull Context context, @StyleRes int themeResId) {
        super(context, resolveDialogTheme(context, themeResId));
        mAlert = new AlertController(getContext(), this, getWindow());
    }

AlertController控制的佈局。

public AlertController(Context context, AppCompatDialog di, Window window) {
        mContext = context;
        mDialog = di;
        mWindow = window;
        mHandler = new ButtonHandler(di);

        final TypedArray a = context.obtainStyledAttributes(null, R.styleable.AlertDialog,
                R.attr.alertDialogStyle, 0);

        mAlertDialogLayout = a.getResourceId(R.styleable.AlertDialog_android_layout, 0);
        mButtonPanelSideLayout = a.getResourceId(R.styleable.AlertDialog_buttonPanelSideLayout, 0);

        mListLayout = a.getResourceId(R.styleable.AlertDialog_listLayout, 0);
        mMultiChoiceItemLayout = a.getResourceId(R.styleable.AlertDialog_multiChoiceItemLayout, 0);
        mSingleChoiceItemLayout = a
                .getResourceId(R.styleable.AlertDialog_singleChoiceItemLayout, 0);
        mListItemLayout = a.getResourceId(R.styleable.AlertDialog_listItemLayout, 0);
        mShowTitle = a.getBoolean(R.styleable.AlertDialog_showTitle, true);

        a.recycle();

        /* We use a custom title so never request a window title */
        di.supportRequestWindowFeature(Window.FEATURE_NO_TITLE);
    }

可以看到各種自定義屬性，是用R.styleable.AlertDialog獲取的。打開android系統values搜索AlertDialog:

可以看到有一個style的屬性，與AlertDialog的R.styleable.AlertDialog自定義屬性是對應的，說明可以控制UI樣式。

		<item name="android:layout">@layout/abc_alert_dialog_material</item>
        <item name="listLayout">@layout/abc_select_dialog_material</item>
        <item name="listItemLayout">@layout/select_dialog_item_material</item>
        <item name="multiChoiceItemLayout">@layout/select_dialog_multichoice_material</item>
        <item name="singleChoiceItemLayout">@layout/select_dialog_singlechoice_material</item>

打開@layout/abc_alert_dialog_material：

<?xml version="1.0" encoding="utf-8"?>
<!--
     Copyright (C) 2015 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.
-->

<android.support.v7.widget.AlertDialogLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/parentPanel"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:gravity="start|left|top"
    android:orientation="vertical">

    <include layout="@layout/abc_alert_dialog_title_material"/>

    <FrameLayout
        android:id="@+id/contentPanel"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:minHeight="48dp">

        <View android:id="@+id/scrollIndicatorUp"
              android:layout_width="match_parent"
              android:layout_height="1dp"
              android:layout_gravity="top"
              android:background="?attr/colorControlHighlight"
              android:visibility="gone"/>

        <android.support.v4.widget.NestedScrollView
            android:id="@+id/scrollView"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:clipToPadding="false">

            <LinearLayout
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:orientation="vertical">

                <android.support.v4.widget.Space
                    android:id="@+id/textSpacerNoTitle"
                    android:layout_width="match_parent"
                    android:layout_height="@dimen/abc_dialog_padding_top_material"
                    android:visibility="gone"/>

                <TextView
                    android:id="@android:id/message"
                    style="@style/TextAppearance.AppCompat.Subhead"
                    android:layout_width="match_parent"
                    android:layout_height="wrap_content"
                    android:paddingLeft="?attr/dialogPreferredPadding"
                    android:paddingRight="?attr/dialogPreferredPadding"/>

                <android.support.v4.widget.Space
                    android:id="@+id/textSpacerNoButtons"
                    android:layout_width="match_parent"
                    android:layout_height="@dimen/abc_dialog_padding_top_material"
                    android:visibility="gone"/>
            </LinearLayout>
        </android.support.v4.widget.NestedScrollView>

        <View android:id="@+id/scrollIndicatorDown"
              android:layout_width="match_parent"
              android:layout_height="1dp"
              android:layout_gravity="bottom"
              android:background="?attr/colorControlHighlight"
              android:visibility="gone"/>

    </FrameLayout>

    <FrameLayout
        android:id="@+id/customPanel"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:minHeight="48dp">

        <FrameLayout
            android:id="@+id/custom"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"/>
    </FrameLayout>

    <include layout="@layout/abc_alert_dialog_button_bar_material"
             android:layout_width="match_parent"
             android:layout_height="wrap_content"/>

</android.support.v7.widget.AlertDialogLayout>

最下面include了一個layout點進去：

<?xml version="1.0" encoding="utf-8"?>
<!--
     Copyright (C) 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.
-->

<ScrollView xmlns:android="http://schemas.android.com/apk/res/android"
            android:id="@+id/buttonPanel"
            style="?attr/buttonBarStyle"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:fillViewport="true"
            android:scrollIndicators="top|bottom">

    <android.support.v7.widget.ButtonBarLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:gravity="bottom"
        android:layoutDirection="locale"
        android:orientation="horizontal"
        android:paddingBottom="4dp"
        android:paddingLeft="12dp"
        android:paddingRight="12dp"
        android:paddingTop="4dp">

        <Button
            android:id="@android:id/button3"
            style="?attr/buttonBarNeutralButtonStyle"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"/>

        <android.support.v4.widget.Space
            android:id="@+id/spacer"
            android:layout_width="0dp"
            android:layout_height="0dp"
            android:layout_weight="1"
            android:visibility="invisible"/>

        <Button
            android:id="@android:id/button2"
            style="?attr/buttonBarNegativeButtonStyle"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"/>

        <Button
            android:id="@android:id/button1"
            style="?attr/buttonBarPositiveButtonStyle"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"/>

    </android.support.v7.widget.ButtonBarLayout>

</ScrollView>

button2和button1就是AlertDialog的取消和確定按鈕。樣式分別用了buttonBarNegativeButtonStyle和buttonBarPositiveButtonStyle兩個style。搜索這兩個style發現：

<item name="buttonBarStyle">@style/Widget.AppCompat.ButtonBar</item>
	<item name="buttonBarButtonStyle">@style/Widget.AppCompat.Button.ButtonBar.AlertDialog</item>
        <item name="buttonBarPositiveButtonStyle">?attr/buttonBarButtonStyle</item>
        <item name="buttonBarNegativeButtonStyle">?attr/buttonBarButtonStyle</item>
        <item name="buttonBarNeutralButtonStyle">?attr/buttonBarButtonStyle</item>

那麼我們只需要在自己的主題重新定buttonBarNegativeButtonStyle和buttonBarPositiveButtonStyle兩個style就可以修改按鈕樣式了。
看下效果：

我修改的樣式：

<resources>

    <!-- Base application theme. -->
    <style name="AppTheme" parent="Theme.AppCompat.Light.DarkActionBar">
        <!-- Customize your theme here. -->
        <item name="colorPrimary">@color/colorPrimary</item>
        <item name="colorPrimaryDark">@color/colorPrimaryDark</item>
        <item name="colorAccent">@color/colorAccent</item>

        <item name="buttonBarPositiveButtonStyle">@style/positiveBtnStyle</item>
        <item name="buttonBarNegativeButtonStyle">@style/negativeBtnstyle</item>

    </style>

    <!--確定按鈕樣式-->
    <style name="positiveBtnStyle" parent="Widget.AppCompat.Button.ButtonBar.AlertDialog">
        <item name="android:textColor">#0000ff</item>
    </style>

    <!--取消按鈕樣式-->
    <style name="negativeBtnstyle" parent="Widget.AppCompat.Button.ButtonBar.AlertDialog">
        <item name="android:textColor">#999999</item>
    </style>


</resources>


AlertDialog.Builder builder = new AlertDialog.Builder(this);
        builder.setMessage("你確定要把這5塊錢捐給紅十字會嗎？")
                .setTitle("標題")
                .setNegativeButton("取消",null)
                .setPositiveButton("確定",null)
                .show();