DialogFragment内存泄露最强解决方案

一、为什么要使用DialogFragment:
在程序开发中我们经常要做一些弹窗提醒，如果用自带的Dialog虽然能解决一部分，但强大的UI是不会给你这个机会的，各种自定义UI,时间选择器弹窗，巴拉巴拉~~~
使用DialogFragment就是能配合一些工具进行自定义，同时官方也是比较推荐使用，极大方便了开发,比如自定义一个baseDialogFragment.

package com.gzjiequan.rescuewithyou.customwidget;

import android.app.Dialog;
import android.os.Bundle;
import android.util.DisplayMetrics;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.view.Window;

import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.fragment.app.DialogFragment;

import com.gzjiequan.rescuewithyou.R;
import com.zhy.autolayout.utils.AutoUtils;

import butterknife.ButterKnife;
import butterknife.Unbinder;

/**
 * @author Wudi
 * @date 2019/4/16
 */
public abstract class BaseDialogFragment extends DialogFragment {
    protected String TAG = this.getClass().getSimpleName();
    private static final String SAVED_DIALOG_STATE_TAG = "android:savedDialogState";
    Unbinder unbinder;

    @Override
    public void onActivityCreated(@Nullable Bundle savedInstanceState) {
        super.onActivityCreated(savedInstanceState);
        if (getDialog() != null) {
            try {
                // 解决Dialog内D存泄漏
                getDialog().setOnDismissListener(null);
                getDialog().setOnCancelListener(null);
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    }

    @Override
    public void onStart() {
        super.onStart();
        // 全屏显示Dialog，重新测绘宽高
        if (getDialog() != null) {
            DisplayMetrics dm = new DisplayMetrics();
            getActivity().getWindowManager().getDefaultDisplay().getMetrics(dm);
            getDialog().getWindow().setLayout(ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.WRAP_CONTENT);
        }
    }

    @Override
    public void onPause() {
        super.onPause();
    }

    @Override
    public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        View rootView = inflater.inflate(getLayoutResId(), container, false);
        AutoUtils.auto(rootView);
        unbinder = ButterKnife.bind(this, rootView);
        initView();
        return rootView;
    }

    /**
     * 获取布局文件
     *
     * @return
     */
    protected abstract int getLayoutResId();

    /**
     * 初始化界面
     */
    protected void initView() {
    }

    @Override
    public void onDestroyView() {
        super.onDestroyView();
        unbinder.unbind();
    }


    /**
     * 全屏显示Dialog
     *
     * @param savedInstanceState
     * @return
     */
    @NonNull
    @Override
    public Dialog onCreateDialog(@Nullable Bundle savedInstanceState) {
        Dialog dialog = new Dialog(getActivity());
        dialog.requestWindowFeature(Window.FEATURE_NO_TITLE);
        dialog.getWindow().setBackgroundDrawableResource(R.color.transparent);
        dialog.setCanceledOnTouchOutside(false);
        dialog.setCancelable(false);
        return dialog;
    }

}

二、内存泄漏的原因：
根据源码分析到的是，DialogFragment的dialog的变量Handler对DialogFragment持有。

QQ图片20190610162758.jpg

源码如下：

    Dialog(@NonNull Context context, @StyleRes int themeResId, boolean createContextThemeWrapper) {
        if (createContextThemeWrapper) {
            if (themeResId == ResourceId.ID_NULL) {
                final TypedValue outValue = new TypedValue();
                context.getTheme().resolveAttribute(R.attr.dialogTheme, outValue, true);
                themeResId = outValue.resourceId;
            }
            mContext = new ContextThemeWrapper(context, themeResId);
        } else {
            mContext = context;
        }

        mWindowManager = (WindowManager) context.getSystemService(Context.WINDOW_SERVICE);

        final Window w = new PhoneWindow(mContext);
        mWindow = w;
        w.setCallback(this);
        w.setOnWindowDismissedCallback(this);
        w.setOnWindowSwipeDismissedCallback(() -> {
            if (mCancelable) {
                cancel();
            }
        });
        w.setWindowManager(mWindowManager, null, null);
        w.setGravity(Gravity.CENTER);

        mListenersHandler = new ListenersHandler(this);
    }

    private static final class ListenersHandler extends Handler {
        private final WeakReference<DialogInterface> mDialog;

        public ListenersHandler(Dialog dialog) {
            mDialog = new WeakReference<>(dialog);
        }

        @Override
        public void handleMessage(Message msg) {
            switch (msg.what) {
                case DISMISS:
                    ((OnDismissListener) msg.obj).onDismiss(mDialog.get());
                    break;
                case CANCEL:
                    ((OnCancelListener) msg.obj).onCancel(mDialog.get());
                    break;
                case SHOW:
                    ((OnShowListener) msg.obj).onShow(mDialog.get());
                    break;
            }
        }
    }
 /**
     * Set a listener to be invoked when the dialog is canceled.
     *
     * <p>This will only be invoked when the dialog is canceled.
     * Cancel events alone will not capture all ways that
     * the dialog might be dismissed. If the creator needs
     * to know when a dialog is dismissed in general, use
     * {@link #setOnDismissListener}.</p>
     * 
     * @param listener The {@link DialogInterface.OnCancelListener} to use.
     */
    public void setOnCancelListener(@Nullable OnCancelListener listener) {
        if (mCancelAndDismissTaken != null) {
            throw new IllegalStateException(
                    "OnCancelListener is already taken by "
                    + mCancelAndDismissTaken + " and can not be replaced.");
        }
        if (listener != null) {
            mCancelMessage = mListenersHandler.obtainMessage(CANCEL, listener);
        } else {
            mCancelMessage = null;
        }
    }

    /**
     * Set a message to be sent when the dialog is canceled.
     * @param msg The msg to send when the dialog is canceled.
     * @see #setOnCancelListener(android.content.DialogInterface.OnCancelListener)
     */
    public void setCancelMessage(@Nullable Message msg) {
        mCancelMessage = msg;
    }

    /**
     * Set a listener to be invoked when the dialog is dismissed.
     * @param listener The {@link DialogInterface.OnDismissListener} to use.
     */
    public void setOnDismissListener(@Nullable OnDismissListener listener) {
        if (mCancelAndDismissTaken != null) {
            throw new IllegalStateException(
                    "OnDismissListener is already taken by "
                    + mCancelAndDismissTaken + " and can not be replaced.");
        }
        if (listener != null) {
            mDismissMessage = mListenersHandler.obtainMessage(DISMISS, listener);
        } else {
            mDismissMessage = null;
        }
    }

但一般在DialogFragment的源码默认实现了对dialog的取消和结束的监听：

  @Override
    public void onActivityCreated(@Nullable Bundle savedInstanceState) {
        super.onActivityCreated(savedInstanceState);

        if (!mShowsDialog) {
            return;
        }

        View view = getView();
        if (view != null) {
            if (view.getParent() != null) {
                throw new IllegalStateException(
                        "DialogFragment can not be attached to a container view");
            }
            mDialog.setContentView(view);
        }
        final Activity activity = getActivity();
        if (activity != null) {
            mDialog.setOwnerActivity(activity);
        }
        mDialog.setCancelable(mCancelable);
        mDialog.setOnCancelListener(this);
        mDialog.setOnDismissListener(this);
        if (savedInstanceState != null) {
            Bundle dialogState = savedInstanceState.getBundle(SAVED_DIALOG_STATE_TAG);
            if (dialogState != null) {
                mDialog.onRestoreInstanceState(dialogState);
            }
        }
    }

网上有些分析是直接置为空，但是根本不能解决问题，在super.onActivityCreated(savedInstanceState)中仍然会handler先持有DialogFragment,

    @Override
    public void onActivityCreated(@Nullable Bundle savedInstanceState) {
        super.onActivityCreated(savedInstanceState);
        if (getDialog() != null) {
            try {
                // 解决Dialog内D存泄漏
                getDialog().setOnDismissListener(null);
                getDialog().setOnCancelListener(null);
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    }

最终解决方案：

 @Override
    public void onActivityCreated(@Nullable Bundle savedInstanceState) {
        if (getShowsDialog()) {
            setShowsDialog(false);
        }
        super.onActivityCreated(savedInstanceState);
        setShowsDialog(true);

        View view = getView();
        if (view != null) {
            if (view.getParent() != null) {
                throw new IllegalStateException(
                        "DialogFragment can not be attached to a container view");
            }
            getDialog().setContentView(view);
        }
        final Activity activity = getActivity();
        if (activity != null) {
            getDialog().setOwnerActivity(activity);
        }
        if (savedInstanceState != null) {
            Bundle dialogState = savedInstanceState.getBundle(SAVED_DIALOG_STATE_TAG);
            if (dialogState != null) {
                getDialog().onRestoreInstanceState(dialogState);
            }
        }
    }