Thread: Facing a problem in android studio ( java )

Moved to Android Section.

Where is the problem?
Is it in the IDE trying to compile the program? Copy the error messages here.
Or when there is a clean compile and you try executing the app in a device?
If when executing, are there any error messages in the logcat console?

the problem is that launcher stops working. No it happens while testing on physical device only ( emulator is rly slow ).

package com.simcoder.novalauncherclone;
 
import android.content.Context;
import android.support.annotation.NonNull;
import android.support.v4.view.PagerAdapter;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.GridView;
 
 
import java.util.ArrayList;
 
public class ViewPagerAdapter extends PagerAdapter {
 
    Context context;
    ArrayList<PagerObject> pagerAppList;
    int cellHeight, numColumn;
    ArrayList<com.simcoder.novalauncherclone.AppAdapter> appAdapterList = new ArrayList<>();
 
    public ViewPagerAdapter(Context context, ArrayList<PagerObject> pagerAppList, int cellHeight, int numColumn){
        this.context = context;
        this.pagerAppList = pagerAppList;
        this.cellHeight = cellHeight;
        this.numColumn = numColumn;
    }
 
    @NonNull
    @Override
    public Object instantiateItem(@NonNull ViewGroup container, int position) {
        LayoutInflater inflater = LayoutInflater.from(context);
        ViewGroup layout = (ViewGroup) inflater.inflate(R.layout.pager_layout, container, false);
 
        final GridView mGridView = layout.findViewById(R.id.grid);
        mGridView.setNumColumns(numColumn);
 
        com.simcoder.novalauncherclone.AppAdapter mGridAdapter = new com.simcoder.novalauncherclone.AppAdapter(context, pagerAppList.get(position).getAppList(), cellHeight);
        mGridView.setAdapter(mGridAdapter);
 
        appAdapterList.add(mGridAdapter);
 
        container.addView(layout);
        return layout;
    }
 
    @Override
    public void destroyItem(@NonNull ViewGroup container, int position, @NonNull Object object) {
        container.removeView((View) object);
    }
 
    @Override
    public int getCount() {
        return pagerAppList.size();
    }
 
    @Override
    public boolean isViewFromObject(@NonNull View view, @NonNull Object object) {
        return view == object;
    }
 
    public void notifyGridChanged(){
        for(int i = 0; i < appAdapterList.size();i++){
            appAdapterList.get(i).notifyDataSetChanged();
        }
    }
}

launcher stops working

What is shown in the logcat?

First 4 lessons were cool, but after that with some new lines of code + new folders etc. launcher just stopped working.

What has been changed from when the app was working?


Please edit your post and wrap your code with code tags:

[code]
**YOUR CODE GOES HERE**
[/code]

to get highlighting and preserve formatting.

Can you look at the logcat to see if there are errors?

To copy the logcat to a file on your PC
Connect the device to the PC
On Windows, Run this command:
<Path to adv.exe file>adb.exe logcat >> LogcatFile.txt

No problem. I'm here every day.

Hi there I've been thinking about my problem for a long long time. I found some mistakes by myself and now the launcher is working fine, but I am not sure 100% that it will never crash cause code still has some issues. Would you take a look at java classes ?

Damn, in android emulator its crashing..Tested on physical device and it was working really good with no erros or crashes Should I just leave these emulators and keep going with my physical device?

in android emulator its crashing

Are there error messages in the logcat?

I don't know why it would work in the device and not the emulator. Are they running different versions of Android?

Can not really remember now, I will check it in 30 mins Yes they're running different versions of android ( 7.0 on physical device ) and 5.0 on emulator.

Here is erros while running emulator without anything.

Emulator: Warning: Quick Boot / Snapshots not supported on this machine. A CPU with EPT + UG features is currently needed. We will address this in a future release.

18:40 Emulator: dsound: Could not initialize ADC

18:40 Emulator: dsound: Could not create capture buffer

18:40 Emulator: dsound: Reason: An undetermined error occurred inside the DirectSound subsystem

18:40 Emulator: dsound: Could not initialize ADC

18:40 Emulator: dsound: Could not create capture buffer

18:40 Emulator: dsound: Reason: An undetermined error occurred inside the DirectSound subsystem

18:40 Emulator: audio: Failed to create voice `goldfish_audio_in'

18:40 Emulator: C:\Users\User\AppData\Local\Android\Sdk\emulator\q emu\windows-x86_64\qemu-system-armel.exe: warning: opening audio input failed

java.lang.ClassCastException: android.app.Application cannot be cast to com.example.user.emnilauncher.MainActivity
at com.example.user.emnilauncher.AppAdapter$2.onLongC lick(AppAdapter.java:67)

Looks like the code at line 67 is doing an invalid cast.

Is that in some of the new code you added?

Yes sir. Here it is :

package com.example.user.emnilauncher;
 
import android.content.Context;
import android.content.Intent;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.ImageView;
import android.widget.LinearLayout;
import android.widget.TextView;
 
import java.util.List;
 
public class AppAdapter extends BaseAdapter {
    Context context;
    List<AppObject> appList;
    int cellHeight;
 
    public AppAdapter(Context context, List<AppObject> appList, int cellHeight) {
        this.context = context;
        this.appList = appList;
        this.cellHeight = cellHeight;
    }
 
    @Override
    public int getCount() {
        return appList.size();
    }
 
 
    @Override
    public Object getItem(int position) {
        return appList.get(position);
    }
 
    @Override
    public long getItemId(int position) {
        return position;
    }
 
    @Override
    public View getView(final int position, View convertView, ViewGroup parent) {
        View v;
        if (convertView == null) {
            LayoutInflater inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
            v = inflater.inflate(R.layout.item_app, parent, false);
        } else {
            v = convertView;
        }
 
        LinearLayout mLayout = v.findViewById(R.id.layout);
        ImageView mImage = v.findViewById(R.id.image);
        TextView mLabel = v.findViewById(R.id.label);
        LinearLayout.LayoutParams lp = new LinearLayout.LayoutParams(LinearLayout.LayoutParams.WRAP_CONTENT, cellHeight);
        mLayout.setLayoutParams(lp);
 
        mImage.setImageDrawable(appList.get(position).getImage());
        mLabel.setText(appList.get(position).getName());
 
        mLayout.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                ((MainActivity) context).itemPress(appList.get(position));
            }
        });
        mLayout.setOnLongClickListener(new View.OnLongClickListener() {
            @Override
            public boolean onLongClick(View v) {
                ((MainActivity) context).itemLongPress(appList.get(position));
                return false;
            }
        });
        return v;
    }
}

But there is nothing wrong with it as I see..

Please edit your post and wrap your code with code tags: (Not Quote tags)

[code]
**YOUR CODE GOES HERE**
[/code]

to get highlighting and preserve formatting.

Which line is line 67?

Why is context being cast to MainActivity?

        mLayout.setOnLongClickListener(new View.OnLongClickListener() {

this is line 67

--- Update ---

here is MainActivity :

package com.example.user.emnilauncher;
 
import android.content.Intent;
import android.content.pm.ResolveInfo;
import android.graphics.Point;
import android.graphics.drawable.Drawable;
import android.support.annotation.NonNull;
import android.support.design.widget.BottomSheetBehavior;
import android.support.v4.view.ViewPager;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.view.WindowManager;
import android.widget.GridView;
 
import java.lang.reflect.Array;
import java.util.ArrayList;
import java.util.List;
 
public class MainActivity extends AppCompatActivity {
    boolean isBottom = true;
    ViewPager mViewPager;
    int cellHeight;
 
    int NUMBER_OF_ROWS = 5;
    int DRAWER_PEEK_HEIGHT = 100;
 
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        getSupportActionBar().hide();
 
 
        initializeHome();
        initializeDrawer();
    }
 
    ViewPagerAdapter mViewPagerAdapter;
    private void initializeHome() {
        ArrayList<PagerObject> pagerAppList = new ArrayList<>();
 
        ArrayList<AppObject> appList1 = new ArrayList<>();
        ArrayList<AppObject> appList2 = new ArrayList<>();
        ArrayList<AppObject> appList3 = new ArrayList<>();
 
        for (int i = 0; i < 20 ; i++)
            appList1.add(new AppObject("", "", getResources().getDrawable(R.drawable.ic_launcher_foreground)));
        for (int i = 0; i < 20 ; i++)
            appList2.add(new AppObject("", "", getResources().getDrawable(R.drawable.ic_launcher_foreground)));
        for (int i = 0; i < 20 ; i++)
            appList3.add(new AppObject("", "", getResources().getDrawable(R.drawable.ic_launcher_foreground)));
 
        pagerAppList.add(new PagerObject(appList1));
        pagerAppList.add(new PagerObject(appList2));
        pagerAppList.add(new PagerObject(appList3));
 
        cellHeight = (getDisplayContentHeight()- DRAWER_PEEK_HEIGHT) / NUMBER_OF_ROWS;
 
 
        mViewPager = findViewById(R.id.viewPager);
        mViewPagerAdapter = (new ViewPagerAdapter(this, pagerAppList, cellHeight));
        mViewPager.setAdapter(mViewPagerAdapter);
 
    }
 
 
 
    List<AppObject> installedAppList = new ArrayList<>();
     GridView mDrawerGridView;
     BottomSheetBehavior mBottomSheetBehavior;
    private void initializeDrawer() {
        View mBottomSheet = findViewById(R.id.bottomSheet);
        mDrawerGridView = findViewById(R.id.drawerGrid);
        mBottomSheetBehavior = BottomSheetBehavior.from(mBottomSheet);
        mBottomSheetBehavior.setHideable(false);
        mBottomSheetBehavior.setPeekHeight(DRAWER_PEEK_HEIGHT);
 
        installedAppList = getInstalledAppList();
 
        mDrawerGridView.setAdapter(new AppAdapter(getApplicationContext(), installedAppList, cellHeight));
 
        mBottomSheetBehavior.setBottomSheetCallback(new BottomSheetBehavior.BottomSheetCallback() {
            @Override
            public void onStateChanged(@NonNull View bottomSheet, int newState) {
 
                if(mAppDrag != null)
                    return;
                if(newState == BottomSheetBehavior.STATE_COLLAPSED&& mDrawerGridView.getChildAt(0).getY() != 0)
                mBottomSheetBehavior.setState(BottomSheetBehavior.STATE_EXPANDED);
                if(newState == BottomSheetBehavior.STATE_DRAGGING && mDrawerGridView.getChildAt(0).getY() != 0)
                    mBottomSheetBehavior.setState(BottomSheetBehavior.STATE_EXPANDED);
            }
 
            @Override
            public void onSlide(@NonNull View bottomSheet, float slideOffSet) {
 
            }
        });
 
    }
 
 
    AppObject mAppDrag = null;
    public void itemPress(AppObject app) {
        if (mAppDrag != null) {
 
            app.setPackageName(mAppDrag.getPackageName());
            app.setName(mAppDrag.getName());
            app.setImage(mAppDrag.getImage());
            mAppDrag = null;
            mViewPagerAdapter.notifyGridChanged();
            return;
        }else{
            Intent launchAppIntent = getApplicationContext().getPackageManager().getLaunchIntentForPackage(app.getPackageName());
            if (launchAppIntent != null)
                getApplicationContext().startActivity(launchAppIntent);
        }
    }
 
 
    public void itemLongPress(AppObject app){
        collapseDrawer();
        mAppDrag = app;
    }
    private void collapseDrawer() {
        mDrawerGridView.setY(0);
        mBottomSheetBehavior.setState(BottomSheetBehavior.STATE_COLLAPSED);
    }
 
 
 
 
 
 
 
    private List<AppObject> getInstalledAppList() {
        List<AppObject> list = new ArrayList<>();
 
        Intent intent = new Intent(Intent.ACTION_MAIN, null);
        intent.addCategory(Intent.CATEGORY_LAUNCHER);
        List<ResolveInfo> untreatedAppList = getApplicationContext().getPackageManager().queryIntentActivities(intent, 0);
 
        for(ResolveInfo untreatedApp : untreatedAppList) {
            String appName = untreatedApp.activityInfo.loadLabel(getPackageManager()).toString();
            String appPackageName = untreatedApp.activityInfo.packageName;
            Drawable appImage = untreatedApp.activityInfo.loadIcon(getPackageManager());
            AppObject app = new AppObject(appPackageName, appName, appImage);
            if (!list.contains(app))
                list.add(app);
        }
        return list;
    }
    private int getDisplayContentHeight() {
        final WindowManager windowManager = getWindowManager();
        final Point size = new Point();
        int screenHeight = 0, actionBarHeight= 0, statusBarHeight = 0;
        if (getActionBar()!= null){
            actionBarHeight = getActionBar().getHeight();
        }
        int resourceId = getResources().getIdentifier("status_bar_height", "dimen", "android")  ;
        if(resourceId > 0){
            statusBarHeight = getResources().getDimensionPixelSize(resourceId);
        }
        int contentTop = (findViewById(android.R.id.content).getTop());
        windowManager.getDefaultDisplay().getSize(size);
        screenHeight = size.y;
        return screenHeight - contentTop - actionBarHeight - statusBarHeight;
    }
}

Glad that I fixed it by myself again! Coding is awesome!

this is line 67

There isn't a cast on that line. The error message says: android.app.Application cannot be cast to com.example.user.emnilauncher.MainActivity.
So I would expect to see the cast with (MainActivity) on line 67.

Why does the code do a cast there?

can't understand logcat errors

The lines with the error message looks like the lines that come from the printStackTrace method. That is standard java output.

My question is about this line of code(which could be line 67):
((MainActivity) context).itemPress(appList.get(position));

Why is context cast to MainActivity?

Have you fixed the problem now?