Android Studio 功能的警報對話框在另一個 java class

Question

在我的MainActivity.Java中，我在一個按鈕中有一個onClickListener ，當它被點擊時會顯示一個警報對話框

scanbtn.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            View scanPopup = getLayoutInflater().inflate(R.layout.scan_tab, null);

            forScan.setView(scanPopup);
            dialog = forScan.create();
            dialog.show();

        }
    });

這是ScanTab.Java ，其中 AlertDialog 將具有其功能

package com.example.AppDraft1.activity;

import android.app.PendingIntent;
import android.content.Intent;
import android.nfc.NdefMessage;
import android.nfc.NdefRecord;
import android.nfc.NfcAdapter;
import android.nfc.Tag;
import android.nfc.tech.MifareClassic;
import android.nfc.tech.MifareUltralight;
import android.os.Bundle;
import android.os.Parcelable;
import android.provider.Settings;
import android.widget.TextView;
import android.widget.Toast;

import androidx.appcompat.app.AppCompatActivity;

import com.example.AppDraft1.MainActivity;
import com.example.AppDraft1.R;
import com.example.AppDraft1.parser.NdefMessageParser;
import com.example.AppDraft1.record.ParsedNdefRecord;

import java.util.List;

public class ScanTab extends AppCompatActivity {

    private NfcAdapter nfcAdapter;
    private PendingIntent pendingIntent;
    private TextView text;
    private String first, surname, id;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.scan_tab);
        text = (TextView) findViewById(R.id.text);
        nfcAdapter = NfcAdapter.getDefaultAdapter(this);

        if (nfcAdapter == null) {
            Toast.makeText(this, "No NFC", Toast.LENGTH_SHORT).show();
            finish();
            return;
        }

        pendingIntent = PendingIntent.getActivity(this, 0,
                new Intent(this, this.getClass())
                        .addFlags(Intent.FLAG_ACTIVITY_SINGLE_TOP), 0);
    }


    @Override
    protected void onResume() {
        super.onResume();
        if (nfcAdapter != null) {
            if (!nfcAdapter.isEnabled())
                showWirelessSettings();

            nfcAdapter.enableForegroundDispatch(this, pendingIntent, null, null);
        }
    }


    @Override
    protected void onPause() {
        super.onPause();
        if (nfcAdapter != null){
            nfcAdapter.disableForegroundDispatch(this);
        }
    }

    @Override
    protected void onNewIntent(Intent intent) {
        super.onNewIntent(intent);
        setIntent(intent);
        resolveIntent(intent);
    }

    private void resolveIntent(Intent intent) {
        String action = intent.getAction();

        if (NfcAdapter.ACTION_TAG_DISCOVERED.equals(action)
                || NfcAdapter.ACTION_TECH_DISCOVERED.equals(action)
                || NfcAdapter.ACTION_NDEF_DISCOVERED.equals(action)) {
            Parcelable[] rawMsgs = intent.getParcelableArrayExtra(NfcAdapter.EXTRA_NDEF_MESSAGES);
            NdefMessage[] msgs;

            if (rawMsgs != null) {
                msgs = new NdefMessage[rawMsgs.length];

                for (int i = 0; i < rawMsgs.length; i++) {
                    msgs[i] = (NdefMessage) rawMsgs[i];
                }

            } else {
                byte[] empty = new byte[0];
                byte[] id = intent.getByteArrayExtra(NfcAdapter.EXTRA_ID);
                Tag tag = (Tag) intent.getParcelableExtra(NfcAdapter.EXTRA_TAG);
                byte[] payload = dumpTagData(tag).getBytes();
                NdefRecord record = new NdefRecord(NdefRecord.TNF_UNKNOWN, empty, id, payload);
                NdefMessage msg = new NdefMessage(new NdefRecord[] {record});
                msgs = new NdefMessage[] {msg};
            }

            displayMsgs(msgs);
        }
    }

    private void displayMsgs(NdefMessage[] msgs) {
        if (msgs == null || msgs.length == 0)
            return;

        StringBuilder builder = new StringBuilder();
        List<ParsedNdefRecord> records = NdefMessageParser.parse(msgs[0]);
        final int size = records.size();

        for (int i = 0; i < size; i++) {
            ParsedNdefRecord record = records.get(i);
            String str = record.str();
            builder.append(str).append("\n");
        }

        text.setText(builder.toString());
        Toast.makeText(this, "NFC Tag Detected", Toast.LENGTH_SHORT).show();

        sndData();
    }
    public void sndData(){

        String theText = text.getText().toString();

        //split data
        String[] split = theText.split("/",3);
        first = split[0];     //first name
        surname = split[1];   //surname
        id = split[2];        //id number

        Intent intent = new Intent(ScanTab.this, MainActivity.class);
        intent.putExtra("FName", first);
        intent.putExtra("SName", surname);
        intent.putExtra("ID", id);
        startActivity(intent);
    }

    private void showWirelessSettings() {
        Toast.makeText(this, "You need to enable NFC", Toast.LENGTH_SHORT).show();
        Intent intent = new Intent(Settings.ACTION_WIRELESS_SETTINGS);
        startActivity(intent);
    }

    private String dumpTagData(Tag tag) {
        StringBuilder sb = new StringBuilder();
        byte[] id = tag.getId();
        sb.append("ID (hex): ").append(toHex(id)).append('\n');
        sb.append("ID (reversed hex): ").append(toReversedHex(id)).append('\n');
        sb.append("ID (dec): ").append(toDec(id)).append('\n');
        sb.append("ID (reversed dec): ").append(toReversedDec(id)).append('\n');

        String prefix = "android.nfc.tech.";
        sb.append("Technologies: ");
        for (String tech : tag.getTechList()) {
            sb.append(tech.substring(prefix.length()));
            sb.append(", ");
        }

        sb.delete(sb.length() - 2, sb.length());

        for (String tech : tag.getTechList()) {
            if (tech.equals(MifareClassic.class.getName())) {
                sb.append('\n');
                String type = "Unknown";

                try {
                    MifareClassic mifareTag = MifareClassic.get(tag);

                    switch (mifareTag.getType()) {
                        case MifareClassic.TYPE_CLASSIC:
                            type = "Classic";
                            break;
                        case MifareClassic.TYPE_PLUS:
                            type = "Plus";
                            break;
                        case MifareClassic.TYPE_PRO:
                            type = "Pro";
                            break;
                    }
                    sb.append("Mifare Classic type: ");
                    sb.append(type);
                    sb.append('\n');

                    sb.append("Mifare size: ");
                    sb.append(mifareTag.getSize() + " bytes");
                    sb.append('\n');

                    sb.append("Mifare sectors: ");
                    sb.append(mifareTag.getSectorCount());
                    sb.append('\n');

                    sb.append("Mifare blocks: ");
                    sb.append(mifareTag.getBlockCount());
                } catch (Exception e) {
                    sb.append("Mifare classic error: " + e.getMessage());
                }
            }

            if (tech.equals(MifareUltralight.class.getName())) {
                sb.append('\n');
                MifareUltralight mifareUlTag = MifareUltralight.get(tag);
                String type = "Unknown";
                switch (mifareUlTag.getType()) {
                    case MifareUltralight.TYPE_ULTRALIGHT:
                        type = "Ultralight";
                        break;
                    case MifareUltralight.TYPE_ULTRALIGHT_C:
                        type = "Ultralight C";
                        break;
                }
                sb.append("Mifare Ultralight type: ");
                sb.append(type);
            }
        }

        return sb.toString();
    }

    private String toHex(byte[] bytes) {
        StringBuilder sb = new StringBuilder();
        for (int i = bytes.length - 1; i >= 0; --i) {
            int b = bytes[i] & 0xff;
            if (b < 0x10)
                sb.append('0');
            sb.append(Integer.toHexString(b));
            if (i > 0) {
                sb.append(" ");
            }
        }
        return sb.toString();
    }

    private String toReversedHex(byte[] bytes) {
        StringBuilder sb = new StringBuilder();
        for (int i = 0; i < bytes.length; ++i) {
            if (i > 0) {
                sb.append(" ");
            }
            int b = bytes[i] & 0xff;
            if (b < 0x10)
                sb.append('0');
            sb.append(Integer.toHexString(b));
        }
        return sb.toString();
    }

    private long toDec(byte[] bytes) {
        long result = 0;
        long factor = 1;
        for (int i = 0; i < bytes.length; ++i) {
            long value = bytes[i] & 0xffl;
            result += value * factor;
            factor *= 256l;
        }
        return result;
    }

    private long toReversedDec(byte[] bytes) {
        long result = 0;
        long factor = 1;
        for (int i = bytes.length - 1; i >= 0; --i) {
            long value = bytes[i] & 0xffl;
            result += value * factor;
            factor *= 256l;
        }
        return result;


    }
}

當我測試它時，視圖正在工作，但功能不存在。 如何在 AlertDialog 中嵌入或使這些功能正常工作？

Answer 1

警報對話框旨在“提醒”用戶某事，或在輸入對話框的情況下根據用戶的輸入運行代碼。 如果要在 alert 對話框中運行代碼，可以在對話框的 setView 之前運行。

此外，不建議使用警報對話框阻止用戶與應用程序交互。

如果您想在另一個活動中運行代碼，在您的情況下，從 MainActivity 在 ScanActivity 中運行代碼，我能想到的最好方法是 Activity RESULTS API 替換 StartActivityForResult [閱讀此處]

但我只是建議您啟動 ScanActivity 並從那里顯示對話框，然后您可以輕松調用 ScanActivity 的所有方法。