ScanningActivity 泄漏了 IntentReceiver，然后出现 NullPointException

Question

我正在致力于实现打印收据的应用程序。 我使用 Printooth 库来实现此实现，但遇到了 2 个无法继续的问题。 我有如下所示的按钮，当我单击它时，首先搜索并让您与蓝牙设备配对，然后当配对时再次单击，打印一些文本。 问题有 2 个，按顺序排列有：

1. `E/ActivityThread：活动 com.mazenrashed.printooth.ui.ScanningActivity 泄露了最初在此处注册的 IntentReceiver com.mazenrashed.printooth.utilities.Bluetooth$3@dd8369f。您是否错过了对 unregisterReceiver() 的调用？ android.app.IntentReceiverLeaked：活动 com.mazenrashed.printooth.ui.ScanningActivity 泄露了最初在此处注册的 IntentReceiver com.mazenrashed.printooth.utilities.Bluetooth$3@dd8369f。您是否错过了对 unregisterReceiver() 的调用？

2. ---------崩溃开始 E/AndroidRuntime：致命异常：main 进程：com.example.testaapplication0209，PID：3667 java.lang.NullPointerException：尝试在空对象引用上调用虚拟方法“void com.mazenrashed.printooth.utilities.Printing.print(java.util.ArrayList)”

完整代码：

package com.example.testaapplication0209;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;

import com.mazenrashed.printooth.Printooth;
import com.mazenrashed.printooth.data.printable.Printable;
import com.mazenrashed.printooth.data.printable.RawPrintable;
import com.mazenrashed.printooth.data.printable.TextPrintable;
import com.mazenrashed.printooth.data.printer.DefaultPrinter;
import com.mazenrashed.printooth.ui.ScanningActivity;
import com.mazenrashed.printooth.utilities.Printing;
import com.mazenrashed.printooth.utilities.PrintingCallback;

import java.util.ArrayList;

import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;

public class PrintActivity extends AppCompatActivity {
private Printing printing = null;
private PrintingCallback printingCallback = null;
private Button button;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_print);

    if (Printooth.INSTANCE.hasPairedPrinter())
        printing = Printooth.INSTANCE.printer();
    initViews();
    initListeners();

    button = findViewById(R.id.button);
    button.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            if (!Printooth.INSTANCE.hasPairedPrinter())
                startActivityForResult(new Intent(PrintActivity.this, ScanningActivity.class), ScanningActivity.SCANNING_FOR_PRINTER);
            else
                printText();
        }
    });
}

private void initListeners() {
    if (printing!=null && printingCallback==null) {
        Log.d("xxx", "initListeners ");
        printingCallback = new PrintingCallback() {

            public void connectingWithPrinter() {
                Toast.makeText(getApplicationContext(), "Connecting with printer", Toast.LENGTH_SHORT).show();
                Log.d("xxx", "Connecting");
            }
            public void printingOrderSentSuccessfully() {
                Toast.makeText(getApplicationContext(), "printingOrderSentSuccessfully", Toast.LENGTH_SHORT).show();
                Log.d("xxx", "printingOrderSentSuccessfully");

            }
            public void connectionFailed(@NonNull String error) {
                Toast.makeText(getApplicationContext(), "connectionFailed :"+error, Toast.LENGTH_SHORT).show();
                Log.d("xxx", "connectionFailed : "+error);
            }
            public void onError(@NonNull String error) {
                Toast.makeText(getApplicationContext(), "onError :"+error, Toast.LENGTH_SHORT).show();
                Log.d("xxx", "onError : "+error);
            }
            public void onMessage(@NonNull String message) {
                Toast.makeText(getApplicationContext(), "onMessage :" +message, Toast.LENGTH_SHORT).show();
                Log.d("xxx", "onMessage : "+message);
            }
        };

        Printooth.INSTANCE.printer().setPrintingCallback(printingCallback);
    }
}
private void initViews() {
    if (Printooth.INSTANCE.getPairedPrinter()!=null)
        Toast.makeText(getApplicationContext(), (Printooth.INSTANCE.hasPairedPrinter())?("Un-pair "+ Printooth.INSTANCE.getPairedPrinter().getName()):"Pair with printer", Toast.LENGTH_SHORT).show();
}

private void printText() {
    ArrayList<Printable> printables = new ArrayList<>();
    printables.add(new RawPrintable.Builder(new byte[]{27, 100, 4}).build());

    //Add Text
    printables.add(new TextPrintable.Builder()
            .setText("Hello World: Jagadeesh")
            .setCharacterCode(DefaultPrinter.Companion.getCHARCODE_PC1252())
            .setNewLinesAfter(1)
            .build());

    printables.add((new TextPrintable.Builder())
            .setText(" Hello World : été è à '€' içi Bò Xào Coi Xanh")
            .setCharacterCode(DefaultPrinter.Companion.getCHARCODE_PC1252())
            .setNewLinesAfter(1)
            .build());

    //Custom Text
    printables.add((new TextPrintable.Builder())
            .setText("Hello World")
            .setLineSpacing(DefaultPrinter.Companion.getLINE_SPACING_60())
            .setAlignment(DefaultPrinter.Companion.getALIGNMENT_CENTER())
            .setEmphasizedMode(DefaultPrinter.Companion.getEMPHASIZED_MODE_BOLD())
            .setUnderlined(DefaultPrinter.Companion.getUNDERLINED_MODE_ON())
            .setNewLinesAfter(1)
            .build());

    printing.print(printables);
}

@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    super.onActivityResult(requestCode, resultCode, data);
    Log.d("xxx", "onActivityResult "+requestCode);

    if (requestCode == ScanningActivity.SCANNING_FOR_PRINTER && resultCode == Activity.RESULT_OK) {
        initListeners();
    }
    initViews();
}

}

我还有一个应用程序类，并且在manifest.xml中得到所有许可

现在谁能解决这个问题吗？

`

Answer 1

您设置了应用程序课程吗？如果不： 在主包中定义一个应用程序类（ApplicationClass.java）并初始化 Printooth 引擎，如下所示；

public class ApplicationClass extends Application {
    @Override
    public void onCreate() {
        super.onCreate();
        // Use class name (ApplicationClass.this) instead of "this" reference
        // I experienced a failure using "this" reference 
        Printooth.INSTANCE.init(ApplicationClass.this);
    }
}