android：點擊按鈕后應用程序崩潰

Question

您好，我是 android 應用程序開發和 Java 的新手。 我使用了一些來自互聯網的代碼以及 Android Studio 生成的代碼。 它需要通過套接字將字符串發送到 wifi 屏蔽罩來控制裝有貨物的小船。 當我調試我的應用程序時它會啟動，但是當我單擊任何按鈕時它會崩潰。 我嘗試使用 logcat 來查找問題，但它沒有顯示任何內容。 我使用了一些我在 stackoverflow 上找到的錯誤范圍，它是在設備上設置的。 當我嘗試 seekBar 時，應用程序不會崩潰，並且單擊后不會顯示吐司。

在我對代碼進行檢查后，我發現了這一點：

“公共”方法 buttonConnectOnClickListener() 未通過第 69 行的接口公開

它向我展示了每個按鈕偵聽器上的相同問題，但我不知道如何解決它。

這是 Main.java：

    package tomasbenco.kop_android_controller;

    import android.app.Activity;
    import android.content.Context;
    import android.net.ConnectivityManager;
    import android.net.NetworkInfo;
    import android.os.Bundle;
    import android.view.View;
    import android.widget.Button;
    import android.widget.SeekBar;
    import android.widget.Switch;
    import android.widget.Toast;

    import java.io.DataOutputStream;
    import java.io.IOException;
    import java.net.Socket;
    import java.net.UnknownHostException;

    public class Main extends Activity {
        private Button C1Button = null;
        private Button C2Button = null;
        private Switch lightsSwitch = null;
        private SeekBar RESB = null;
        private SeekBar LESB = null;
        private Boolean connected = Boolean.FALSE;
        private DataOutputStream dataOutputStream = null;
        private Socket socket = null;
        private char[] transferReg = new char[7];

    private void setTransferReg(char transferReg, int i) {
        this.transferReg[i] = transferReg;
    }

    private char[] getTransferReg() {
        return transferReg;
    }

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        C1Button = (Button) findViewById(R.id.C1Button);
        C2Button = (Button) findViewById(R.id.C2Button);
        lightsSwitch = (Switch) findViewById(R.id.LightsSwitch);
        RESB = (SeekBar) findViewById(R.id.REseekBar);
        LESB = (SeekBar) findViewById(R.id.LEseekBar);
    }

    private void changeConnectionStatus(Boolean isConnected) {
        connected = isConnected;
        if (isConnected) {
            C1Button.setVisibility(View.VISIBLE);
            C2Button.setVisibility(View.VISIBLE);
            lightsSwitch.setVisibility(View.VISIBLE);
            RESB.setVisibility(View.VISIBLE);
            LESB.setVisibility(View.VISIBLE);
        } else {
            C1Button.setVisibility(View.INVISIBLE);
            C2Button.setVisibility(View.INVISIBLE);
            lightsSwitch.setVisibility(View.INVISIBLE);
            RESB.setVisibility(View.INVISIBLE);
            LESB.setVisibility(View.INVISIBLE);
        }
    }


    public void buttonConnectOnClickListener(View view) {
        ConnectivityManager connectivity = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
        NetworkInfo wifiInfo = connectivity.getNetworkInfo(ConnectivityManager.TYPE_WIFI);
        if (wifiInfo.isConnected()) {
            if (!connected) {
                try {
                    socket = new Socket("192.168.137.1", 55555);
                    Toast msg = Toast.makeText(Main.this,
                            "Connected Successfully", Toast.LENGTH_LONG);
                    msg.show();
                    dataOutputStream = new DataOutputStream(socket.getOutputStream());
                    changeConnectionStatus(Boolean.TRUE);
                } catch (IOException e) {
                    changeConnectionStatus(Boolean.FALSE);
                }
            } else {
                try {
                    socket.close();
                    Toast msg = Toast.makeText(Main.this, "Disconnected Successfully", Toast.LENGTH_LONG);
                    msg.show();
                    changeConnectionStatus(Boolean.FALSE);
                } catch (UnknownHostException e) {
                    changeConnectionStatus(Boolean.FALSE);
                } catch (IOException e) {
                    changeConnectionStatus(Boolean.FALSE);
                }
            }
        } else {
            Toast msg = Toast.makeText(Main.this, "Wifi is not connected !", Toast.LENGTH_LONG);
            msg.show();
        }
    }


    public void C1ButtonOnClickListener(View view) {
        if (C1Button.isActivated()) {
            Toast msg = Toast.makeText(Main.this, "Front cargo bay is opening !", Toast.LENGTH_LONG);
            msg.show();
            transfer_REG(4, '1');
        } else {
            Toast msg = Toast.makeText(Main.this, "Front cargo bay is closing !", Toast.LENGTH_LONG);
            msg.show();
            transfer_REG(4, '0');
        }
    }

    public void C2ButtonOnClickListener(View view) {
        if (C2Button.isActivated()) {
            Toast msg = Toast.makeText(Main.this, "Back cargo bay is opening !", Toast.LENGTH_LONG);
            msg.show();
            transfer_REG(5, '1');
        } else {
            Toast msg = Toast.makeText(Main.this, "Back cargo bay is closing !", Toast.LENGTH_LONG);
            msg.show();
            transfer_REG(5, '0');
        }
    }

    public void lightsButtonOnClickListener(View view) {
        if (C2Button.isActivated()) {
            Toast msg = Toast.makeText(Main.this, "Back cargo bay is opening !", Toast.LENGTH_LONG);
            msg.show();
            transfer_REG(6, '1');
        } else {
            Toast msg = Toast.makeText(Main.this, "Back cargo bay is closing !", Toast.LENGTH_LONG);
            msg.show();
            transfer_REG(6, '0');
        }
    }

    private void transfer_REG(int i, char trans) {
        setTransferReg(trans, i);
        String transfer = new String(getTransferReg());
        if (connected) try {
            dataOutputStream.writeChars(transfer);
        } catch (IOException ignored) {
        }
    }

    public void REListener(View view) {
        if (RESB.getProgress() < 10) {
            transfer_REG(2, Integer.toString(RESB.getProgress()).charAt(0));
            transfer_REG(3, '1');
        } else {
            transfer_REG(2, Integer.toString(RESB.getProgress() - 10).charAt(0));
            transfer_REG(3, '0');
        }
    }

    public void LEListener(View view) {
        if (LESB.getProgress() < 10) {
            transfer_REG(1, Integer.toString(LESB.getProgress()).charAt(0));
            transfer_REG(2, '1');
            Toast msg = Toast.makeText(Main.this, "Left engine power is: -" + Integer.toString(LESB.getProgress()).charAt(0), Toast.LENGTH_LONG);
            msg.show();
        } else {
            transfer_REG(1, Integer.toString(LESB.getProgress() - 10).charAt(0));
            transfer_REG(2, '0');
            Toast msg = Toast.makeText(Main.this, "Left engine power is: " + Integer.toString(LESB.getProgress() - 10).charAt(0), Toast.LENGTH_LONG);
            msg.show();
        }
    }
}

這是 Main.xml：

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
style="@android:style/Theme.Holo"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context=".Main">

<TextView
    android:id="@+id/REtView"
    style="@android:style/Theme.Holo"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_above="@+id/REseekBar"
    android:layout_alignParentEnd="true"
    android:text="@string/RE"
    android:textAppearance="?android:attr/textAppearanceLarge"
    android:textColor="#ffaec0ff"
    android:textStyle="bold|italic"
    android:theme="@style/Holo"
    android:visibility="visible" />

<TextView
    android:id="@+id/LEtView"
    style="@android:style/Theme.Holo"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_above="@+id/LEseekBar"
    android:layout_alignParentStart="true"
    android:text="@string/LE"
    android:textAppearance="?android:attr/textAppearanceLarge"
    android:textColor="#ffaec0ff"
    android:textStyle="bold|italic"
    android:theme="@style/Holo"
    android:visibility="visible" />

<SeekBar
    android:id="@+id/LEseekBar"
    style="@android:style/Theme.Holo"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignParentBottom="true"
    android:layout_alignParentStart="true"
    android:layout_toStartOf="@+id/LightsSwitch"
    android:clickable="true"
    android:max="20"
    android:onClick="LEListener"
    android:progress="10"
    android:theme="@style/Holo"
    android:visibility="visible" />

<SeekBar
    android:id="@+id/REseekBar"
    style="@android:style/Theme.Holo"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignEnd="@+id/REtView"
    android:layout_alignParentBottom="true"
    android:layout_toEndOf="@+id/LightsSwitch"
    android:clickable="true"
    android:max="20"
    android:onClick="REListener"
    android:progress="10"
    android:theme="@style/Holo"
    android:visibility="visible" />

<Button
    android:id="@+id/connButton"
    style="@android:style/Theme.Holo"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignParentTop="true"
    android:layout_centerHorizontal="true"
    android:clickable="true"
    android:onClick="buttonConnectOnClickListener"
    android:text="@string/conn"
    android:textColor="#ffaec0ff"
    android:textStyle="normal"
    android:theme="@style/Holo"
    android:typeface="normal"
    android:visibility="visible" />

<Button
    android:id="@+id/C1Button"
    style="@android:style/Theme.Holo"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_centerHorizontal="true"
    android:layout_centerVertical="true"
    android:clickable="true"
    android:onClick="C1ButtonOnClickListener"
    android:text="@string/C1"
    android:textColor="#ffaec0ff"
    android:textStyle="normal"
    android:theme="@style/Holo"
    android:visibility="visible" />

<Button
    android:id="@+id/C2Button"
    style="@android:style/Theme.Holo"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_below="@+id/C1Button"
    android:layout_centerHorizontal="true"
    android:clickable="true"
    android:onClick="C2ButtonOnClickListener"
    android:text="@string/C2"
    android:textColor="#ffaec0ff"
    android:textStyle="normal"
    android:theme="@style/Holo"
    android:visibility="visible" />

<Switch
    android:id="@+id/LightsSwitch"
    style="@android:style/Theme.Holo"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_below="@+id/C2Button"
    android:layout_centerHorizontal="true"
    android:checked="true"
    android:clickable="true"
    android:onClick="lightsButtonOnClickListener"
    android:showText="false"
    android:singleLine="true"
    android:text="@string/light"
    android:textColor="#ffaec0ff"
    android:textStyle="normal"
    android:theme="@style/Holo"
    android:visibility="visible" />

這是 manifest.xml：

<?xml version="1.0" encoding="utf-8"?>

<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />

<application
    android:allowBackup="true"
    android:icon="@mipmap/ic_launcher"
    android:label="@string/app_name"
    android:theme="@android:style/Theme.Holo">
    <activity
        android:name=".Main"
        android:configChanges="keyboard|keyboardHidden"
        android:label="@string/app_name">
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />

            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>
</application>

Answer 1

試試下面的代碼，

像其余兩個按鈕一樣全局聲明按鈕；

private Button connButton;

將此代碼放在您聲明所有 ID 的位置。

connButton = (Button) findViewById(R.id.connButton);

Answer 2

你能在你的 android manifest 中看到你是否有這個權限嗎？

<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"/>

我試圖復制您的代碼並執行，這就是我使用頂部按鈕遇到的問題。 一旦將其添加到 Android 清單中，問題就解決了。

由於您沒有發布 AndroidManifest.xml，因此很難說您可能在那里聲明了哪個權限。 那么您可以檢查一下是否已經存在，如果沒有，您可以添加並嘗試嗎？

我希望這有幫助。