Android底部弹窗实现方案

项目中经常会遇到底部弹窗，例如分享弹窗等，今天就来把底部弹窗实现方案总结一下。

BottomSheetDialog

底部表单样式的对话框基类。依赖于Behavior机制。

依赖

dependencies {
    implementation 'com.google.android.material:material:1.4.0'
}

基类封装

public abstract class BaseBottomSheetDialog extends BottomSheetDialog {

    public BaseBottomSheetDialog(@NonNull Context context) {
        super(context, R.style.Theme_BottomSheetDialog_Base);
    }

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        setContentView(getLayoutResId());

        initView();
    }

    @Override
    protected void onStart() {
        super.onStart();

        changePeekHeight();

        Window window = getWindow();
        if (window != null) {
            window.setLayout(WindowManager.LayoutParams.MATCH_PARENT, getPeekHeight());
            window.setGravity(Gravity.BOTTOM | Gravity.CENTER_HORIZONTAL);
        }
    }

    private void changePeekHeight() {
        final int peekHeight = getPeekHeight();
        if (peekHeight > 0) {
            View bottomSheet = findViewById(com.google.android.material.R.id.design_bottom_sheet);
            BottomSheetBehavior<View> behavior = BottomSheetBehavior.from(bottomSheet);
            // 设置是否可拖拽
            behavior.setDraggable(isDraggable());
            behavior.setPeekHeight(peekHeight);
            // 解决平板上宽度无法填满问题
            behavior.setMaxWidth(Resources.getSystem().getDisplayMetrics().widthPixels);
            ViewGroup.LayoutParams layoutParams = bottomSheet.getLayoutParams();
            if (isFixHeight()) {
            	layoutParams.height = peekHeight;
            }
            bottomSheet.setLayoutParams(layoutParams);
        }
    }
	
	protected boolean isDraggable() {
        return true;
    }

    protected boolean isFixHeight() {
        return true;
    }

    protected abstract int getLayoutResId();

    protected abstract void initView();

    protected int getPeekHeight() {
        return WindowManager.LayoutParams.WRAP_CONTENT;
    }
}

为了去掉BottomSheetDialog默认的背景，需要修改主题样式：

 <style name="Theme.BottomSheetDialog.Base" parent="Theme.Design.Light.BottomSheetDialog">
     "bottomSheetStyle">@style/BottomSheetDialogStyle
 style>

 <style name="BottomSheetDialogStyle" parent="Widget.Design.BottomSheet.Modal">
     "android:background">@android:color/transparent
 style>

除此之外，如果需要对生命周期进行感知或者自动恢复，还可以使用BottomSheetDialogFragment作为继承基类。

小技巧：如果设置了PeekHeight以后需要设置最大可展开高度，只需要在根布局设置android:maxHeight属性即可

自定义Dialog

继承Dialog实现自定义弹窗。

public abstract class BaseBottomDialog extends AppCompatDialog {

    public BaseBottomDialog(Context context) {
        super(context, R.style.Theme_BottomDialog_Base);
    }

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        setContentView(getLayoutResId());

        initView();
    }

    @Override
    protected void onStart() {
        super.onStart();

        Window window = getWindow();
        if (window != null) {
            window.setLayout(WindowManager.LayoutParams.MATCH_PARENT, getPeekHeight());
            window.setGravity(Gravity.BOTTOM | Gravity.CENTER_HORIZONTAL);
        }
    }

    protected abstract int getLayoutResId();

    protected abstract void initView();

    protected int getPeekHeight() {
        return WindowManager.LayoutParams.WRAP_CONTENT;
    }
}

为了去掉弹窗自带的背景，需要自定义主题样式：

 <style name="Theme.BottomDialog.Base" parent="android:style/Theme.Dialog">
        "android:windowBackground">@android:color/transparent
        "android:windowNoTitle">true
        "android:windowIsFloating">true
        "android:windowContentOverlay">@null
        "android:windowAnimationStyle">@style/Animation.BottomDialog
    style>

    <style name="Animation.BottomDialog" parent="Animation.AppCompat.Dialog">
        "android:windowEnterAnimation">@anim/design_bottom_sheet_slide_in
        "android:windowExitAnimation">@anim/design_bottom_sheet_slide_out
    style>

其中的弹窗动画样式为：

design_bottom_sheet_slide_in

<set xmlns:android="http://schemas.android.com/apk/res/android"
    android:duration="@integer/bottom_sheet_slide_duration"
    android:interpolator="@android:anim/accelerate_decelerate_interpolator">

  <translate
      android:fromYDelta="20%p"
      android:toYDelta="0"/>

  <alpha
      android:fromAlpha="0.0"
      android:toAlpha="1.0"/>

set>

design_bottom_sheet_slide_out

<set xmlns:android="http://schemas.android.com/apk/res/android"
    android:duration="@integer/bottom_sheet_slide_duration"
    android:interpolator="@android:anim/accelerate_interpolator">

  <translate
      android:fromYDelta="0"
      android:toYDelta="20%p"/>

  <alpha
      android:fromAlpha="1.0"
      android:toAlpha="0.0"/>

set>

WindowManager

通过WindowManager添加视图到窗口的方式。

public abstract class BaseBottomPanel {

    protected Context context;

    private WindowManager mWindowManager;
    private WindowManager.LayoutParams mParams;

    private boolean mShowing = false;

    private View mView;

    public BaseBottomPanel(Context context) {
        this.context = context;
        mWindowManager = (WindowManager) context.getSystemService(Context.WINDOW_SERVICE);
    }

    public void show() {
        if (!mShowing) {
            inflate();
            try {
                mWindowManager.addView(mView, mParams);
                mShowing = true;
            } catch (Exception e) {
                mShowing = false;
                return;
            }
        }

        initView();
    }

    public void dismiss() {
        if (mShowing) {
            try {
                mWindowManager.removeView(mView);
                mShowing = false;
            } catch (Exception e) {
                mShowing = true;
            }
        }
    }

    private void inflate() {
        mView = LayoutInflater.from(context).inflate(getLayoutResId(), null);

        mParams = new WindowManager.LayoutParams();
        mParams.gravity = Gravity.BOTTOM | Gravity.CENTER_HORIZONTAL;
        mParams.format = PixelFormat.TRANSLUCENT;
        mParams.type = WindowManager.LayoutParams.TYPE_APPLICATION_ATTACHED_DIALOG;
        mParams.flags = WindowManager.LayoutParams.FLAG_DIM_BEHIND
                | WindowManager.LayoutParams.FLAG_LAYOUT_IN_SCREEN
                | WindowManager.LayoutParams.FLAG_LAYOUT_NO_LIMITS;
        mParams.windowAnimations = R.style.Animation_BottomDialog;
        mParams.width = WindowManager.LayoutParams.MATCH_PARENT;
        mParams.height = getPeekHeight();
        mParams.dimAmount = 0.6f;
    }

    public Context getContext() {
        return context;
    }

    protected <T extends View> T findViewById(@IdRes int id) {
        if (mView == null) {
            return null;
        }
        return mView.findViewById(id);
    }

    protected abstract int getLayoutResId();

    protected abstract void initView();

    protected int getPeekHeight() {
        return WindowManager.LayoutParams.WRAP_CONTENT;
    }
}

窗口动画为：

 <style name="Animation.BottomDialog" parent="Animation.AppCompat.Dialog">
     "android:windowEnterAnimation">@anim/design_bottom_sheet_slide_in
     "android:windowExitAnimation">@anim/design_bottom_sheet_slide_out
 style>

PopupWindow

通过PopWindow指定Gravity为Bottom来实现底部弹窗、

PopupWindow popupWindow = new PopupWindow();
View view = LayoutInflater.from(this).inflate(R.layout.dialog_share, null);
popupWindow.setContentView(view);
popupWindow.setWidth(WindowManager.LayoutParams.MATCH_PARENT);
popupWindow.setHeight(WindowManager.LayoutParams.WRAP_CONTENT);
popupWindow.setBackgroundDrawable(new ColorDrawable(Color.TRANSPARENT));
popupWindow.showAtLocation(findViewById(android.R.id.content), Gravity.BOTTOM, 0, 0);

以上只是个人总结的部分基类封装或实现，有需要的可以自行拷贝并进行修改以契合个人需求，同时也希望能给个赞，谢谢。

感谢大家的支持，如有错误请指正，如需转载请标明原文出处！