App behaves differently on different devices - android-studio

Question

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I created an App and when I run it on a Motorola Xoom it executes the main activity as I expected but when I run it on a Huawei phone it displays Hello World and never executes the main activity. (Android 4.1.2 and 8 respectively. I have created projects using the Basic Activity and the Empty Activity and get the same result with both). How do I stop the Hello World?
package com.example.xoom;
import android.hardware.usb.UsbConstants;
import android.os.Bundle;
import androidx.appcompat.app.AppCompatActivity;
import android.app.PendingIntent;
import android.content.Intent;
import android.text.SpannableString;
import android.text.Spanned;
import android.text.style.ForegroundColorSpan;
import android.text.style.RelativeSizeSpan;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.RelativeLayout;
import android.widget.Spinner;
import android.widget.TextView;
import android.widget.Button;
import android.content.Context;
import android.hardware.usb.UsbManager;
import android.hardware.usb.UsbDevice;
import android.hardware.usb.UsbDeviceConnection;
import android.hardware.usb.UsbEndpoint;
import android.hardware.usb.UsbInterface;
import android.graphics.Color;
import android.graphics.Typeface;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.HashMap;
public class MainActivity extends AppCompatActivity
{
final Button[] pitchButton = new Button[50];
int startLength;
#Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
String ACTION_USB_PERMISSION = "com.example.xoom";
byte[] sendChar = {0x5A}; // ASCII "Z"
byte[] getChar = new byte[200];
boolean addListener;
TextView tv = new TextView(this);
int buttonCount = 0;
for (int i = 0; i < 50; i++)
{
pitchButton[i] = new Button(this);
pitchButton[i].setTypeface(Typeface.MONOSPACE);
}
tv.setTextSize(20);
getWindow().getDecorView().setBackgroundColor(Color.CYAN);
UsbManager manager = (UsbManager) getSystemService(Context.USB_SERVICE);
if (manager.getDeviceList().isEmpty()) // The device list is empty
{
tv.setTextColor(Color.RED);
tv.append("No USB Devices Found");
}
else
{
tv.setTextColor(Color.BLUE);
HashMap<String, UsbDevice> deviceList = manager.getDeviceList();
Iterator<UsbDevice> deviceIterator = deviceList.values().iterator();
UsbDevice device = deviceIterator.next(); // Get first device in list
PendingIntent pi = PendingIntent.getBroadcast(this, 0,
new Intent(ACTION_USB_PERMISSION), 0);
manager.requestPermission(device, pi);
UsbDeviceConnection connection = manager.openDevice(device);
getDeviceProperties(device, manager, tv); // Show USB device properties
getInterfaceProperties(device, connection, tv); // Show USB Interface properties
tv.setText(""); // Clear information from above because you don't want to see
// it normally but sometimes you do. Make this statement
// a comment if you do.
setConnectionProperties(connection); // Set speed etc of connection
UsbEndpoint endpointOut = device.getInterface(1).getEndpoint(1);
UsbEndpoint endpointIn = device.getInterface(1).getEndpoint(0);
connection.bulkTransfer(endpointOut, sendChar, 1, 500); // Send request for data
//
// It takes more than one read to get the data out of the FIFO
// Build up message by polling the FIFO until there is nothing left
// This has taken a lot of fiddling about to make it work. The baud
// and the timeouts have to be just so.
// (9600 and 200 work here but why who knows (or cares))
//
int k = 0;
char[] labelStr = new char[20];
int flag = Spanned.SPAN_EXCLUSIVE_EXCLUSIVE;
int bytesReceived = connection.bulkTransfer(endpointIn, getChar, 200, 200);
while (bytesReceived > 0)
{
for (int j = 0; j < bytesReceived; j++)
{
labelStr[k++] = (char) getChar[j];
if (getChar[j] == 13) // Carriage return
{
String label = String.valueOf(labelStr, 1, k - 1);
SpannableString spanLabel = new SpannableString(label);
spanLabel.setSpan(new RelativeSizeSpan(1.0f), 0, spanLabel.length(), flag);
addListener = true;
if (label.contains("Cross Slide"))
{ // Start adding pitches
spanLabel = new SpannableString("Pitch");
spanLabel.setSpan(new ForegroundColorSpan(Color.RED), 0, spanLabel.length(), flag);
addListener = false;
}
if (label.contains("End"))
{ // Start adding lengths
spanLabel = new SpannableString("Length");
spanLabel.setSpan(new ForegroundColorSpan(Color.RED), 0, spanLabel.length(), flag);
addListener = false;
if (startLength == 0) // Avoid the second "End" messages from MCU
startLength = buttonCount;
}
pitchButton[buttonCount].setText(spanLabel);
pitchButton[buttonCount].setId(buttonCount);
if (addListener)
{
pitchButton[buttonCount].setOnClickListener(new View.OnClickListener()
{
#Override
public void onClick(View v)
{
int buttonIndex;
Button buttonText = (Button) v;
String bt = buttonText.getText().toString();
String message;
if (bt.contains(".")) // On Button press display selected value
{
message = "Pitch ";
buttonIndex = 0;
}
else
{
message = "Length ";
buttonIndex = startLength;
}
message = message + bt;
pitchButton[buttonIndex].setText(message);
pitchButton[buttonIndex].setBackgroundColor(Color.GREEN);
}
});
}
buttonCount++;
k = 0;
}
}
bytesReceived = connection.bulkTransfer(endpointIn, getChar, 200, 200);
}
connection.close();
RelativeLayout.LayoutParams[] params = new RelativeLayout.LayoutParams[100];
RelativeLayout rel = new RelativeLayout(this);
rel.addView(tv);
int leftMargin = 0;
int topMargin = 0;
int lineCount = 0;
for (int i = 0; i < buttonCount - 1; i++)
{
params[i] = new RelativeLayout.LayoutParams(
RelativeLayout.LayoutParams.WRAP_CONTENT, RelativeLayout.LayoutParams.WRAP_CONTENT);
params[i].width = 150;
params[i].height = 50;
if (Math.IEEEremainder(lineCount, 5) == 0) // Put 5 buttons per line
{
topMargin = topMargin + params[i].height;
leftMargin = 0;
}
lineCount++;
if (pitchButton[i].getText().toString().contains("Pitch"))
{
topMargin = topMargin + params[i].height;
leftMargin = 0;
lineCount = 0;
}
if (pitchButton[i].getText().toString().contains("Length"))
{
topMargin = topMargin + params[i].height;
leftMargin = 0;
lineCount = 0;
}
params[i].leftMargin = leftMargin;
leftMargin = leftMargin + params[i].width;
params[i].topMargin = topMargin;
pitchButton[i].setLayoutParams(params[i]);
rel.addView(pitchButton[i]);
}
//
//Add control for setting taper
//
ArrayList<String> taperArray = new ArrayList<String>();
taperArray.add("1");
taperArray.add("2");
taperArray.add("3");
Spinner spinner = new Spinner(this,Spinner.MODE_DIALOG);
spinner.setBackgroundColor(Color.BLUE);
String taperPrompt = "Set Taper Angle";
RelativeLayout.LayoutParams spinnerParams = new RelativeLayout.LayoutParams(
RelativeLayout.LayoutParams.WRAP_CONTENT, RelativeLayout.LayoutParams.WRAP_CONTENT);
spinnerParams.width = 50;
spinnerParams.height = 40;
spinnerParams.topMargin = 600;
spinnerParams.leftMargin = 200;
spinner.setPrompt("Select Taper Angle");
spinner.setLayoutParams(spinnerParams);
ArrayAdapter<String> spinnerArrayAdapter = new ArrayAdapter<String>(this, android.R.layout.simple_spinner_dropdown_item, taperArray);
spinner.setAdapter(spinnerArrayAdapter);
spinner.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener()
{
public void onItemSelected(AdapterView<?> adapterView, View view, int i, long l)
{
}
public void onNothingSelected(AdapterView<?> adapterView)
{
}
});
RelativeLayout.LayoutParams taperParams = new RelativeLayout.LayoutParams(
RelativeLayout.LayoutParams.WRAP_CONTENT, RelativeLayout.LayoutParams.WRAP_CONTENT);
taperParams.width = 200;
taperParams.height = 50;
taperParams.topMargin = 600;
taperParams.leftMargin = 10;
TextView taperView = new TextView(this);
taperView.setLayoutParams(taperParams);
taperView.setText(taperPrompt);
taperView.setTextColor(Color.RED);
taperView.setTextSize(20);
rel.addView(taperView);
rel.addView(spinner);
setContentView(rel);
}
}
public void setConnectionProperties(UsbDeviceConnection connection)
{
connection.controlTransfer(0x40, 0, 0, 0, null, 0, 0);// reset
// mConnection.controlTransfer(0×40,
// 0, 1, 0, null, 0,
// 0);//clear Rx
connection.controlTransfer(0x40, 0, 2, 0, null, 0, 0);// clear Tx
connection.controlTransfer(0x40, 0x02, 0x0000, 0, null, 0, 0);// flow
// control
// none
connection.controlTransfer(0x40, 0x03, 0x4138, 0, null, 0, 0);// baudrate
// 9600 (4138 is 9600, 1A is 115200 0271 is 4800)
connection.controlTransfer(0x40, 0x04, 0x0008, 0, null, 0, 0);// data bit
// 8, parity
// none,
// stop bit
// 1, tx off
}
public void getInterfaceProperties(UsbDevice device, UsbDeviceConnection connection, TextView tv)
{
int interfaceCount = device.getInterfaceCount();
int endPointCount;
for (int i=0; i < interfaceCount-1; i++)
{
if (connection.claimInterface(device.getInterface(i), true)) {
tv.append("\nConnection Interface " + i + " Claim succeeded \n");
UsbInterface interfce = device.getInterface(i);
endPointCount = interfce.getEndpointCount();
tv.append("Endpoint count for Interface " + i + " is " + endPointCount + "\n");
for (int j = 0; j < endPointCount; j++) {
if (interfce.getEndpoint(j).getType() == UsbConstants.USB_ENDPOINT_XFER_INT)
tv.append("Endpoint " + j + " Type is Xfer Int \n");
if (interfce.getEndpoint(j).getType() == UsbConstants.USB_ENDPOINT_XFER_BULK)
tv.append("Endpoint " + j + " Type is Bulk Xfer \n");
if (interfce.getEndpoint(j).getDirection() == UsbConstants.USB_DIR_IN)
tv.append("Endpoint " + j + " Direction is IN \n");
if (interfce.getEndpoint(j).getDirection() == UsbConstants.USB_DIR_OUT)
tv.append("Endpoint " + j + " Direction is OUT \n");
tv.append("Max packet size = " + interfce.getEndpoint(j).getMaxPacketSize() + "\n");
}
tv.append("Interface Protocol is " + interfce.getInterfaceProtocol() + "\n");
}
}
}
public void getDeviceProperties(UsbDevice device, UsbManager manager, TextView tv)
{
tv.setTextSize(20);
tv.setTextColor(Color.BLUE);
tv.append("USB Device name = " + device.getDeviceName() + "\n");
tv.append("USB Product Id = " + device.getProductId() + "\n");
tv.append("USB Vendor Id = " + device.getVendorId() + "\n");
tv.append("USB Device Id = " + device.getDeviceId() + "\n");
if (manager.hasPermission(device)) // Can the App access the device ?
{
tv.append("Device Permission = Yes \n");
}
else
{
tv.append("Device Permission = No \n");
}
}
}

Answer 1

I have found the answer – when no USB devices are attached to the phone the message No USB Devices Found could ever be displayed on the screen. By adding the line setContentView(tv) after the line tv.append(“No USB Devices Found”) leaves this message on the screen rather than falling back to the Hello World message. Thank you for looking at it. I would still like to know if it is possible to get rid of the Hello World fragment as it seems totally unnecessary (or maybe it is).