Question

我在运行应用程序时无法实例化活动错误，我在清单文件中声明所有类，然后它也会抛出错误，请你帮我解决这个问题，下面是我的类和清单文件代码

WelcomeActivity.java

public class WelcomeActivity extends AppCompatActivity {

    private ViewPager viewPager;
    private MyViewPagerAdapter myViewPagerAdapter;
    private LinearLayout dotsLayout;
    private TextView[] dots;
    private int[] layouts;
    private Button btnSkip, btnNext;
    private PrefManager prefManager;

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

        // Checking for first time launch - before calling setContentView()
        prefManager = new PrefManager(this);
        if (!prefManager.isFirstTimeLaunch()) {
            launchHomeScreen();
            finish();
        }

        // Making notification bar transparent
        if (Build.VERSION.SDK_INT >= 21) {
            getWindow().getDecorView().setSystemUiVisibility(View.SYSTEM_UI_FLAG_LAYOUT_STABLE | View.SYSTEM_UI_FLAG_LAYOUT_FULLSCREEN);
        }

        setContentView(R.layout.activity_welcome);

        viewPager = (ViewPager) findViewById(R.id.view_pager);
        dotsLayout = (LinearLayout) findViewById(R.id.layoutDots);
        btnSkip = (Button) findViewById(R.id.btn_skip);
        btnNext = (Button) findViewById(R.id.btn_next);


        // layouts of all welcome sliders
        // add few more layouts if you want
        layouts = new int[]{
                R.layout.welcome_slide1,
                R.layout.welcome_slide2,
                R.layout.welcome_slide3,
                R.layout.welcome_slide4};

        // adding bottom dots
        addBottomDots(0);

        // making notification bar transparent
        changeStatusBarColor();

        myViewPagerAdapter = new MyViewPagerAdapter();
        viewPager.setAdapter(myViewPagerAdapter);
        viewPager.addOnPageChangeListener(viewPagerPageChangeListener);

        btnSkip.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                launchHomeScreen();
            }
        });

        btnNext.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                // checking for last page
                // if last page home screen will be launched
                int current = getItem(+1);
                if (current < layouts.length) {
                    // move to next screen
                    viewPager.setCurrentItem(current);
                } else {
                    launchHomeScreen();
                }
            }
        });
    }

    private void addBottomDots(int currentPage) {
        dots = new TextView[layouts.length];

        int[] colorsActive = getResources().getIntArray(R.array.array_dot_active);
        int[] colorsInactive = getResources().getIntArray(R.array.array_dot_inactive);

        dotsLayout.removeAllViews();
        for (int i = 0; i < dots.length; i++) {
            dots[i] = new TextView(this);
            dots[i].setText(Html.fromHtml("&#8226;"));
            dots[i].setTextSize(35);
            dots[i].setTextColor(colorsInactive[currentPage]);
            dotsLayout.addView(dots[i]);
        }

        if (dots.length > 0)
            dots[currentPage].setTextColor(colorsActive[currentPage]);
    }

    private int getItem(int i) {
        return viewPager.getCurrentItem() + i;
    }

    private void launchHomeScreen() {
        prefManager.setFirstTimeLaunch(false);
        startActivity(new Intent(WelcomeActivity.this, SplashActivity.class));
        finish();
    }

    //  viewpager change listener
    ViewPager.OnPageChangeListener viewPagerPageChangeListener = new ViewPager.OnPageChangeListener() {

        @Override
        public void onPageSelected(int position) {
            addBottomDots(position);

            // changing the next button text 'NEXT' / 'GOT IT'
            if (position == layouts.length - 1) {
                // last page. make button text to GOT IT
                btnNext.setText(getString(R.string.start));
                btnSkip.setVisibility(View.GONE);
            } else {
                // still pages are left
                btnNext.setText(getString(R.string.next));
                btnSkip.setVisibility(View.VISIBLE);
            }
        }

        @Override
        public void onPageScrolled(int arg0, float arg1, int arg2) {

        }

        @Override
        public void onPageScrollStateChanged(int arg0) {

        }
    };

    /**
     * Making notification bar transparent
     */
    private void changeStatusBarColor() {
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
            Window window = getWindow();
            window.addFlags(WindowManager.LayoutParams.FLAG_DRAWS_SYSTEM_BAR_BACKGROUNDS);
            window.setStatusBarColor(Color.TRANSPARENT);
        }
    }

    /**
     * View pager adapter
     */
    public class MyViewPagerAdapter extends PagerAdapter {
        private LayoutInflater layoutInflater;

        public MyViewPagerAdapter() {
        }

        @Override
        public Object instantiateItem(ViewGroup container, int position) {
            layoutInflater = (LayoutInflater) getSystemService(Context.LAYOUT_INFLATER_SERVICE);

            View view = layoutInflater.inflate(layouts[position], container, false);
            container.addView(view);

            return view;
        }

        @Override
        public int getCount() {
            return layouts.length;
        }

        @Override
        public boolean isViewFromObject(View view, Object obj) {
            return view == obj;
        }


        @Override
        public void destroyItem(ViewGroup container, int position, Object object) {
            View view = (View) object;
            container.removeView(view);
        }
    }
}

的manifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.slider.intro.introslider">

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <activity android:name=".WelcomeActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <activity android:name=".MainActivity" android:label="@string/title_activity_welcome" android:theme="@style/AppTheme.PopupOverlay">
            </activity>
        <activity android:name=".SplashActivity" android:label="@string/title_activity_welcome" android:theme="@style/AppTheme.PopupOverlay"/>
    </application>

</manifest>

错误

java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.slider.intro.introslider/com.slider.intro.introslider.WelcomeActivity}: java.lang.ClassNotFoundException: Didn't find class "com.slider.intro.introslider.WelcomeActivity" on path: DexPathList[[zip file "/data/app/com.slider.intro.introslider-1/base.apk"],nativeLibraryDirectories=[/data/app/com.slider.intro.introslider-1/lib/arm64, /vendor/lib64, /system/lib64]]

Answer 1

此错误表明您在Manifest中定义的活动不在定义的路径上。使用“com.slider.intro.introslider”包中存在的“WelcomeActivity”类。

要检查这个，请进入“WelcomeActivity”类，因为第一行代码与下面给出的完全相同：

package com.slider.intro.introslider.WelcomeActivity;

如果没有，则必须将“WelcomeActivity”类移动到“com.slider.intro.introslider”包中。

运行应用程序时无法实例化活动错误

1 个答案: