内存问题Android App

Question

When I run my app, it instantly crashes. I used the Android Monitor and it looks like when the app starts it uses more memory than allocated (there is a screenshot below showing this). I have only developed for computers so I didn't worry about memory, but it seems that even two moderately sized arrays pushed it over the limit.

public class MainActivity extends AppCompatActivity {

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

    //input initialization
    final EditText numberInput = (EditText) findViewById(R.id.number_input);
    Button submit = (Button) findViewById(R.id.submit_button);
    Button zero = (Button) findViewById((R.id.resetButton));

    //progress bar initialization
    final ProgressBar progressBars[] = null;
    progressBars[0] = (ProgressBar)findViewById(R.id.progressBar0);
    progressBars[1] = (ProgressBar)findViewById(R.id.progressBar1);
    progressBars[2] = (ProgressBar)findViewById(R.id.progressBar2);
    progressBars[3] = (ProgressBar)findViewById(R.id.progressBar3);
    progressBars[4] = (ProgressBar)findViewById(R.id.progressBar4);
    progressBars[5] = (ProgressBar)findViewById(R.id.progressBar5);
    progressBars[6] = (ProgressBar)findViewById(R.id.progressBar6);
    progressBars[7] = (ProgressBar)findViewById(R.id.progressBar7);
    progressBars[8] = (ProgressBar)findViewById(R.id.progressBar8);
    progressBars[9] = (ProgressBar)findViewById(R.id.progressBar9);
    progressBars[10] = (ProgressBar)findViewById(R.id.progressBar10);
    progressBars[11] = (ProgressBar)findViewById(R.id.progressBar11);
    progressBars[12] = (ProgressBar)findViewById(R.id.progressBar12);
    progressBars[13] = (ProgressBar)findViewById(R.id.progressBar13);
    progressBars[14] = (ProgressBar)findViewById(R.id.progressBar14);
    progressBars[15] = (ProgressBar)findViewById(R.id.progressBar15);
    progressBars[16] = (ProgressBar)findViewById(R.id.progressBar16);
    progressBars[17] = (ProgressBar)findViewById(R.id.progressBar17);

    //variable value initialization
    final TextView textViews[] = null;
    textViews[0] = (TextView)findViewById(R.id.value0);
    textViews[1] = (TextView)findViewById(R.id.value1);
    textViews[2] = (TextView)findViewById(R.id.value2);
    textViews[3] = (TextView)findViewById(R.id.value3);
    textViews[4] = (TextView)findViewById(R.id.value4);
    textViews[5] = (TextView)findViewById(R.id.value5);
    textViews[6] = (TextView)findViewById(R.id.value6);
    textViews[7] = (TextView)findViewById(R.id.value7);
    textViews[8] = (TextView)findViewById(R.id.value8);
    textViews[9] = (TextView)findViewById(R.id.value9);
    textViews[10] = (TextView)findViewById(R.id.value10);
    textViews[11] = (TextView)findViewById(R.id.value11);
    textViews[12] = (TextView)findViewById(R.id.value12);
    textViews[13] = (TextView)findViewById(R.id.value13);
    textViews[14] = (TextView)findViewById(R.id.value14);
    textViews[15] = (TextView)findViewById(R.id.value15);
    textViews[16] = (TextView)findViewById(R.id.value16);
    textViews[17] = (TextView)findViewById(R.id.value17);

    submit.setOnClickListener(new View.OnClickListener()
    {
        @Override
        public void onClick(View v)
        {
            //get string from input and convert it into an integer
            int numberInt = Integer.parseInt(numberInput.getText().toString());
            //set the values of the progress bars
            for(int i = 0; i < progressBars.length; i++)
            {
                progressBars[i].setProgress(numberInt);
            }
            //set the value of the variable display
            for (int i = 0; i < textViews.length; i++)
            {
                textViews[i].setText(numberInt);
            }
        }
    });

    zero.setOnClickListener(new View.OnClickListener()
    {
        @Override
        public void onClick(View v)
        {
            //reset the progress bars to 0
            for(int i = 0; i < progressBars.length; i++)
            {
                progressBars[i].setProgress(0);
            }


            //reset the variable display to "~~~"
            for (int i = 0; i < textViews.length; i++)
            {
                textViews[i].setText("~~~");
            }
        }
    });
}

I have already tried the Help > Edit Custom VM Options... which instead of fixing the issue caused Android Studio to refuse to open. I am new to Java, so am I missing a memory leak, is there a more efficient way to store the items in the two arrays, or do I just need to increase the memory for my app?

Answer 1

You need to learn a little more about basic Java structures.

You are not allocating any memory for your arrays. Java is not like JavaScript - it won't automatically allocate space for array elements you assign to.

final ProgressBar progressBars[] = null;
progressBars[0] = (ProgressBar)findViewById(R.id.progressBar0);

This snippet will fail because the array is null (it has no allocated space for any elements). When you try to assign an element to it, it will throw a NullPointerException . You must allocate the space when you create the array:

final ProgressBar progressBars[] = new ProgressBar[18];
progressBars[0] = (ProgressBar)findViewById(R.id.progressBar0);

My advice would be to run through some Java tutorials first. The comments about viewing Logcat should also be heeded - when your App crashes, it will (usually!) tell you exactly where in your source the crash occurred and why.