<com.teresazl.library.impl.LoadingButton
        android:id="@+id/loading_btn_normal"
        android:layout_width="match_parent"
        android:layout_height="48dp"
        android:text="Send"
        android:gravity="center"
        android:textColor="@android:color/white"
        android:textSize="18sp"
        app:complete_text="DONE" />

    // normal
    normalBtn = (LoadingButton) findViewById(R.id.loading_btn_normal);
    normalBtn.setOnLoadCompleteListener(this);
    normalBtn.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            ...
        }
    });
    
    // complete
    completeBtn = (LoadingButton) findViewById(R.id.loading_btn_complete);
    completeBtn.setProgress(100);

    // error
    errorBtn = (LoadingButton) findViewById(R.id.loading_btn_error);
    errorBtn.setProgress(-1);

    // process
    processBtn = (LoadingButton) findViewById(R.id.loading_btn_process);
    processBtn.setProgress(50);

    public class MainActivity extends AppCompatActivity implements ProcessButton.LoadingListener {
        ....
        ....
        
        normalBtn.setOnLoadingListener(this);
        
        @Override
            public void loadComplete() {
                Toast.makeText(this, "complete", Toast.LENGTH_SHORT).show();
            }
        
            @Override
            public void loadError() {
                Toast.makeText(this, "error", Toast.LENGTH_SHORT).show();
            }
    }