java - Activity 占用大量内存，如何减少？

Question

我有一个使用大约 70 MB 内存的 Activity ，即使我通过调用 finish() 关闭该 Activity ，内存也没有释放。当我再次启动它时，它会增加 70 MB 的内存使用量。它使用数据库，但我不认为数据库是问题所在，因为我在另一个 Activity 中使用数据库并且它只使用 14 MB 内存。这是泄漏内存的类的代码:

package ir.noideaw.aufbau;
import android.graphics.Color;
import android.graphics.drawable.ColorDrawable;
import android.graphics.drawable.GradientDrawable;
import android.os.Build;
import android.os.Bundle;
import android.support.annotation.Nullable;
import android.support.design.widget.AppBarLayout;
import android.support.design.widget.CollapsingToolbarLayout;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;
import android.widget.ListAdapter;
import android.widget.ListView;

import java.util.ArrayList;
import java.util.List;

import ir.noideaw.aufbau.Adapter.UnitAdapter;
import ir.noideaw.aufbau.DatabaseHandler.DatabaseAccess;
import ir.noideaw.aufbau.Model.Unit;


public class ElementInfo extends AppCompatActivity {
    private ImageView elementPic;
    private CollapsingToolbarLayout ct;
    private AppBarLayout appBarLayout;
    private int currentApiVersion;
    private ArrayList<Unit> ovUnitsData;
    private List<String> properties;
    private ListView listView;

    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.element_details);
        initialize();
        Bundle data = getIntent().getExtras();
        final String sy = data.getString("elementSymbol");
        DatabaseAccess database = DatabaseAccess.getInstance(this);
        database.open();
        properties = database.setProperties(sy);
        database.close();
        int atomicNumber = Integer.valueOf(database.getAtomicNumber());
        int id = getResources().getIdentifier("element_" + atomicNumber, "drawable", getPackageName());
        if (id != 0) {
            elementPic.setImageResource(id);
        } else {
            elementPic.setBackgroundColor(Color.parseColor(database.getColor()));
        }
        appBarLayout.addOnOffsetChangedListener(new AppBarLayout.OnOffsetChangedListener() {
            boolean isShow = true;
            int scrollRange = -1;

            @Override
            public void onOffsetChanged(AppBarLayout appBarLayout, int verticalOffset) {
                if (scrollRange == -1) {
                    scrollRange = appBarLayout.getTotalScrollRange();
                }
                if (scrollRange + verticalOffset == 0) {
                    ct.setTitle(sy);
                    isShow = true;
                } else if (isShow) {
                    ct.setTitle(" ");//careful there should be a space between double quote otherwise it wont work
                    isShow = false;
                }
            }
        });
        setUnitsData();
        UnitAdapter adapter = new UnitAdapter(this, ovUnitsData);
        listView.setAdapter(adapter);
        listView.setMinimumHeight(listView.getChildCount()*40);
        currentApiVersion = android.os.Build.VERSION.SDK_INT;
        final int flags = View.SYSTEM_UI_FLAG_LAYOUT_STABLE
                | View.SYSTEM_UI_FLAG_LAYOUT_HIDE_NAVIGATION
                | View.SYSTEM_UI_FLAG_LAYOUT_FULLSCREEN
                | View.SYSTEM_UI_FLAG_HIDE_NAVIGATION
                | View.SYSTEM_UI_FLAG_FULLSCREEN
                | View.SYSTEM_UI_FLAG_IMMERSIVE_STICKY;
        if (currentApiVersion >= Build.VERSION_CODES.KITKAT) {
            getWindow().getDecorView().setSystemUiVisibility(flags);
            final View decorView = getWindow().getDecorView();
            decorView.setOnSystemUiVisibilityChangeListener(new View.OnSystemUiVisibilityChangeListener() {
                @Override
                public void onSystemUiVisibilityChange(int visibility) {
                    if ((visibility & View.SYSTEM_UI_FLAG_FULLSCREEN) == 0) {
                        decorView.setSystemUiVisibility(flags);
                    }
                }
            });
        }
        setListViewHeightBasedOnChildren(listView);
        setListViewDevider(listView);
        listView.setDividerHeight(1);
        System.gc();
    }

    @Override
    public void onBackPressed() {
        finish();
    }

    @Override
    public void onWindowFocusChanged(boolean hasFocus) {
        super.onWindowFocusChanged(hasFocus);
        if (currentApiVersion >= Build.VERSION_CODES.KITKAT && hasFocus) {
            getWindow().getDecorView().setSystemUiVisibility(
                    View.SYSTEM_UI_FLAG_LAYOUT_STABLE
                            | View.SYSTEM_UI_FLAG_LAYOUT_HIDE_NAVIGATION
                            | View.SYSTEM_UI_FLAG_LAYOUT_FULLSCREEN
                            | View.SYSTEM_UI_FLAG_HIDE_NAVIGATION
                            | View.SYSTEM_UI_FLAG_FULLSCREEN
                            | View.SYSTEM_UI_FLAG_IMMERSIVE_STICKY);
        }
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        Runtime.getRuntime().gc();
    }

    private void initialize() {
        elementPic = findViewById(R.id.backdrop);
        ct = findViewById(R.id.collapsing_toolbar);
        appBarLayout = findViewById(R.id.appbar);
        listView = findViewById(R.id.ov_list_view);
        ovUnitsData = new ArrayList<>();
    }

    public static void setListViewHeightBasedOnChildren(ListView listView) {
        ListAdapter listAdapter = listView.getAdapter();
        if (listAdapter == null) {
            // pre-condition
            return;
        }
        int totalHeight = 0;
        for (int i = 0; i < listAdapter.getCount(); i++) {
            View listItem = listAdapter.getView(i, null, listView);
            listItem.measure(0, 0);
            totalHeight += listItem.getMeasuredHeight();
        }
        ViewGroup.LayoutParams params = listView.getLayoutParams();
        params.height = totalHeight + (listView.getDividerHeight() * (listAdapter.getCount() - 1));
        listView.setLayoutParams(params);
        listView.requestLayout();
    }

    public void setListViewDevider(ListView listView){
        listView.setDivider(new ColorDrawable(Color.parseColor("#d4d2d1")));
    }

    private void setUnitsData() {
        String[] array = getResources().getStringArray(R.array.ov);
        for (int i = 0; i < 5; ++i) {
            ovUnitsData.add(new Unit(properties.get(i), array[i]));
        }
    }
}

访问 Android Profiler，它显示 Java 使用了大约 60 MB 的内存。还有布局文件:elements_details.xml:

<?xml version="1.0" encoding="utf-8"?>
<android.support.design.widget.CoordinatorLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:fitsSystemWindows="true">

    <android.support.design.widget.AppBarLayout
        android:id="@+id/appbar"
        android:layout_width="match_parent"
        android:layout_height="320dp"
        android:fitsSystemWindows="true"
        android:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar">

        <android.support.design.widget.CollapsingToolbarLayout
            android:id="@+id/collapsing_toolbar"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:fitsSystemWindows="true"
            app:collapsedTitleGravity="top"
            app:contentScrim="?attr/colorPrimary"
            app:layout_scrollFlags="scroll|exitUntilCollapsed"
            app:titleEnabled="true">

            <ImageView
                android:id="@+id/backdrop"
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                android:fitsSystemWindows="true"
                android:scaleType="centerCrop"
                android:src="@drawable/element_1"
                app:layout_collapseMode="parallax" />

            <RelativeLayout
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:layout_gravity="top"
                android:layout_alignParentBottom="true"
                android:paddingBottom="30dp">

                    <TextView
                        android:id="@+id/element_symbol"
                        android:layout_width="wrap_content"
                        android:layout_height="wrap_content"
                        android:layout_alignParentBottom="true"
                        android:layout_marginLeft="20dp"
                        android:textSize="40dp" />

                    <LinearLayout
                        android:layout_width="wrap_content"
                        android:layout_height="wrap_content"
                        android:layout_alignParentBottom="true"
                        android:layout_toRightOf="@id/element_symbol"
                        android:orientation="vertical">

                        <TextView
                            android:id="@+id/element_name"
                            android:layout_width="wrap_content"
                            android:layout_height="wrap_content"
                            android:layout_alignParentLeft="true"
                            android:textSize="15dp" />

                        <TextView
                            android:id="@+id/element_molar_mass"
                            android:layout_width="wrap_content"
                            android:layout_height="wrap_content"
                            android:layout_alignParentLeft="true"
                            android:textSize="15dp" />
                    </LinearLayout>
            </RelativeLayout>

            <android.support.v7.widget.Toolbar
                android:id="@+id/toolbar"
                android:layout_width="match_parent"
                android:layout_height="?attr/actionBarSize"
                app:layout_collapseMode="pin"
                app:popupTheme="@style/ThemeOverlay.AppCompat.Light" />
        </android.support.design.widget.CollapsingToolbarLayout>
    </android.support.design.widget.AppBarLayout>

    <include layout="@layout/nested_scroll_view" />
</android.support.design.widget.CoordinatorLayout>

nested_scroll_view.xml:

<?xml version="1.0" encoding="utf-8"?>
<android.support.v4.widget.NestedScrollView xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:scrollbars="none"
    app:layout_behavior="@string/appbar_scrolling_view_behavior">

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

        <RelativeLayout style="@style/TitleRelativeLayout">

            <RelativeLayout style="@style/TitleRelativeLayoutInRelativeLayout">

                <ImageView
                    android:id="@+id/atom_image"
                    style="@style/TitleImageView"
                    android:src="@drawable/atom" />

                <TextView
                    style="@style/TitleTextView"
                    android:layout_toLeftOf="@id/atom_image"
                    android:text="@string/overview" />
            </RelativeLayout>
        </RelativeLayout>

        <include layout="@layout/overview"/>
    </LinearLayout>
</android.support.v4.widget.NestedScrollView>

另外，我不认为它与ListView有关，因为当我删除它时，我没有遇到任何差异。如何减少内存使用量？我的目标是 40 MB。更新:Android Profiler-内存:

堆转储:

Answer 1

如果每次启动 Activity 内存消耗都会增加，并且在 Activity 完成时未释放此内存，那么您可能存在内存泄漏。

查看您的代码，我会检查两件事:

不要在此处传递 Activity 引用:

DatabaseAccess database = DatabaseAccess.getInstance(this);

在 onStart() 中执行此操作，然后在 onStop() 中删除监听器:

final View decorView = getWindow().getDecorView();
decorView.setOnSystemUiVisibilityChangeListener(new View.OnSystemUiVisibilityChangeListener() {
            @Override
            public void onSystemUiVisibilityChange(int visibility) {
                if ((visibility & View.SYSTEM_UI_FLAG_FULLSCREEN) == 0) {
                    decorView.setSystemUiVisibility(flags);
                }
            }
        });